When Genius Failed tells the story of Long Term Capital Management, a hedge fund founded by a group of geniuses, highly intelligent and experienced individuals in their field. LTCM was expected to be a leader in a new way of generating profits in the financial markets. Headed by an experienced trader who could generate $500 million per year, two Nobel laureates in Economics, and an expert in risk management, LTCM boasted the intellectual power of the company.

The term "hedge fund" is a colloquialism derived from the expression "to hedge one's bets," meaning to limit the possibility of loss on a speculation by betting on the other side. Initially, LTCM ran smoothly. Using the mathematical models developed by its two Nobel laureates, the company was consistently able to generate profits even when the market was in a bad condition. In 1996, this small company was able to generate a profit of $2.1 billion, an amount that outperformed the profits of large companies such as McDonald's, Disney, Nike, or Gillette.

LTCM itself made money by generating small profits from a large number of trades, but multiplying those "small profits" with the help of leverage (debt) that was up to 30 times their capital. This enabled LTCM to generate large profits with only a minimal price difference. Unfortunately, it was their heavy reliance on debt that led to the downfall of LTCM. When the Russian debt crisis occurred in 1998, which then triggered a panic in the financial markets, LTCM was trapped in a market without buyers. This was exacerbated by the large position of LTCM in every market they entered, making it difficult for them to exit/sell their positions.

Roger Lowenstein successfully produced a historical account of the birth, success, and ultimately the downfall of a financial company that was so confident in its own genius. His writing style is good, and Lowenstein is also able to write about various financial topics, which may not be boring for the layperson, in an easy-to-understand way. The content of this book itself is more like a novel, making it easy to read. Overall, When Genius Failed is a cautionary tale about pride, greed, and the unfairness of a system that favors the wealthy. Because in the end, although LTCM lost billions of dollars and required government intervention, not a single person was punished for the company's mistakes. The founders and those involved were able to walk away and even have the audacity to start a new financial company with the same concept as Long Term Capital Management.

Still pertinent as ever....

Less a Science than Blind Faith

In 1999, just a year before the publication of this book, my brother and I released a similar work titled “The Internet Bubble” (HarperCollins). It held the position of a Business Week bestseller for six months. However, that financial bubble and the subsequent crisis paled in comparison to the magnitude of LTCM.

When our book was in the process of being published, I received word from an editor at Fortune magazine that the author of this book had initially begun writing about the tech bubble but changed direction upon learning of ours. Fortunately, he then went on to pen this masterpiece.

During the original LTCM crisis, I was aware of it but didn't delve into the details until now. I was too preoccupied covering the tech frenzy in Silicon Valley for Red Herring Magazine.

The concept of “efficient market hypothesis” immediately caught my attention in this book. The efficient-market hypothesis (EMH) is a theory in financial economics stating that asset prices fully reflect all available information. Developed by Eugene Fama, it argues that investment instruments always trade at their fair value, making it impossible for investors to buy undervalued stocks or sell overpriced ones. Consequently, some economists claimed financial bubbles were impossible. Others contended that it was a “new economy” and that stock prices could be far out of line relative to a company's value. We did the math. After Yahoo was added to the S&P 500 in early 2000, its paper value nearly doubled. When we plugged that value into our spreadsheet, it showed that Yahoo would need to generate $60 BILLION in revenue within five years to justify its current stock price.

People often brought up these theories in relation to our book. I would laugh and say: “Haven’t you read any history? Human beings are irrational.” (Just look at tulip mania, railroad stock speculation, or betting on bitcoin with no underlying value).

I'm no expert on the nuances of the bond trading that LTCM was involved in, but I can spot false assumptions when I see them. The intricacies of LTCM's academically-driven system earned Myron Scholes and Robert Merton the Nobel Prize for Economics (actually the Swedish Bank Prize) in 1997, a year before their fund went into a free fall that nearly brought down the world economy.

The author accurately diagnoses the problem in these three short excerpts.... “As the English essayist G. K. Chesterton wrote, life is \\"a trap for logicians\\" because it is almost reasonable but not quite; it is usually sensible but occasionally otherwise: \\"It looks just a little more mathematical and regular than it is; its exactitude is obvious, but its inexactitude is hidden; its wildness lies in wait” “Lawrence Summers, now the U.S. Treasury secretary, told The Wall Street Journal after the crash, \\"The efficient market hypothesis is the most remarkable error in the history of economic theory.” \\"After tech entrepreneur, Mitchell Kapor, took Merton's finance course, he decided that quantitative finance was less a science than a faith - a doctrine for ideologues \\"blinded by the power of the model.\\" It appealed to intellectuals who craved a sense of order, but could lead them disastrously astray if markets moved outside the model.”

In the case of LTCM, what fell outside the model was the collapse of Asian markets and Russia following suit, resulting in a crash. Such events are sometimes called “black swans” as they deviate from what is normally expected and are extremely hard to predict. They are typically random and unexpected. The metaphor comes from what Europeans witnessed upon their first arrival in Australia. They believed all swans were white but were shocked to see black swans on that continent.

Our tech bubble book was published in November 1999 with a clear warning of what was to come, but most people disagreed with us. We received one-star reviews on Amazon. Meanwhile, Myron Scholes had moved to San Francisco and become a lecturer at Stanford. But it seemed he still hadn't learned his lesson. In the early months of 2000, I read an interesting snippet in a local paper about a Q & A session at Stanford after a lecture by Scholes. He was asked if there was a tech stock bubble, and he said no. I sent a brief letter to the editor refuting his answer, and it was published. Sure enough, two months later, the prime market for tech stocks, NASDAQ, imploded. The Nobel Prize winner was wrong again.

As a student of the efficient market idea, I have always been curious about what these guys were up to in more detail, even after seeing the Nova program about the meltdown of Long Term Capital Management in 1998. This book is an excellent one that explains as well as possible in a general work of literature less than 300 pages.

There are several lessons here that apparently will not be learned. Mathematical models are based on very good math with many assumptions required to make the computations workable. However, the real world is under no obligation to stay within either the quantitative or temporal boundaries needed for an investment program based on these models to survive in the applicable markets. The quote from Keynes, "Markets can remain irrational longer than you can remain solvent," applies. The technique employed by hedge funds like Long Term only works through very large bets with high leverage. Without these elements, the return is insufficient compared to the costs and risks. Unfortunately, leverage is a double-edged sword. If leveraged 10 to 1, a 10% loss in the asset wipes out the investor. As things go wrong, leverage increases as the base equity declines. In the example, a 5% loss in the asset means a 50% loss to the investor. LTCM was routinely leveraged 20 - 30 to 1 and, of course, much higher, eventually more than 100 to 1 as relentless losses hammered their capital.

Many events that affect investments are truly unpredictable both in terms of their source and their impact when they occur. For example, a small nation defaults or devalues. Maybe it's no big deal. But if the small country defaults in the midst of a larger default by a bigger nation (e.g., Russia), there might be a disproportionate effect larger than the simple sum of the two together, especially if the world's largest players are margined up to the eyeballs on a different outcome when it happens. (Or are tied together by a poorly understood network of derivative contracts that ostensibly hedge the risk but in practice become linked together to become the rock that sinks the world.)

Crisis scenarios are poorly represented in such models, which always predict the future based on the past. In a crisis, linkages occur that are not normally apparent, as the book says correlations converge to one. It was a self-delusion on the part of LTCM partners that there was any true diversity in their bets. While most were hedged, all were essentially the same bet made on similar goods in many locations. They were counting on diversity over thousands of positions to prevent the simple leverage example above from taking them out in the short run of adverse market conditions. But as conditions deteriorated, all of their trades suffered in unison, and LTCM took the full force of leverage against its equity. Another non-mathematical fact is that their markets are a small place full of people, not automatons. Once their distress started to become evident, trading behavior compounded their troubles. Although LTCM's secretiveness, arrogance, and its deal-making practices that skinned safety and profit to the bone for those who helped them finance their trades (e.g., Sholes' "warrant") would account for malicious trading designed to hit them when they were down, that is not the main story. The main story is that their success spawned imitators, who had a twofold effect. One, it reduced the quantity and quality of the opportunities for which their models work as others sought out and bought the same opportunities. Two, when things started to go wrong, the arbitrage departments of their lenders were trying to unload positions virtually identical to those held by LTCM, flooding an inherently thin market and leaving them no good way to liquidate their enormous holdings.

On top of that, they did not know when to quit. After a few years of great success when their chosen market was decaying, partly due to their size and success in it, they looked for ways to apply the model to other investments that were a much poorer fit and eventually started to make "directional" trades, a fancy term for ordinary speculation without any hedge at all, and still leveraged. You may know that buying stock in the US is limited to 2 to 1 leverage. LTCM got around this by using complex derivatives that served as proxies for the actual stock and were not governed by that rule.

Summing up, we have: 1. Sheer hubris. 2. Greed. 3. Plain foolishness (dealing in trades that do not fit the model, where LTCM has no expertise and no real edge, even in principle). 4. Reliance on defective technology.

When it all came apart, LTCM was bought out by a consortium of banks coordinated by the Federal Reserve with no public funds involved. The banks had to be persuaded to do this with great difficulty since they had losing arbitrage units of their own and most figured they had less to lose by LTCM's immediate failure than the sum required for the buyout and a later failure. The fearful unknown that brought them around was what the effects of an LTCM failure would have on markets where their own stock had already lost 40 - 50%, and the very markets where they would have to unload their own LTCM wannabe positions in the near future in the midst of the massive liquidation of LTCM.

At the time, this move was decried by many as something the government should not do or as setting a bad example of a soft landing for the excesses of private enterprise in a free market. But note that no public funds were used; it was only the prestige of the Fed that was used to create a private sector solution to a private sector problem.

Compare that to today when upwards of a trillion dollars of public money will be used to bail out the damage caused by financial institutions, many of the same banks that knowingly bet on LTCM despite the risk as they went on to even larger and more imprudent excesses in pursuit of profit without a sound basis for making it. The LTCM fiasco was a small dress rehearsal for the potential and realized consequences of massive, complex, and poorly understood instruments and unsupervised, unregulated hedge funds, and reckless risk-taking on the part of the financial community. The modern financial world is like a 747 with one engine, no backup systems, and a crew more than a bit unclear on how it works. Everything must work right all the time, or there is a crash with little in between. It is an inherent problem. LTCM committed no crimes, no one went to jail, and it cannot be dismissed as an isolated event due to a rogue operator (as when Russian oligarchs steal the IMF bailout money). This all happened with the best and brightest (and the most arrogant) following the latest principles completely within the law, with the blessing of the great Greenspan, and a maximal embodiment of the spirit of the "free market." It's cleaner than Enron (a rogue), but it still does not work.

The efficient market hypothesis is widely regarded as the most remarkable error in the history of economic theory.

When individuals believe they have accomplished the impossible, such as thinking they can manage complexity, they become blind to factors that don't conform to or conflict with their statistical models. Then, they manage to convince the mob on Wall Street of this lie, allowing greed to amplify it almost without limit until it nearly collapses the entire world economy.

Looking back on the development of this issue, it seems难以置信 that it could have gone so far without any correction. However, such things occur when we continuously erode what is considered tolerable. We can see similar situations today, such as the stock market euphoria versus the COVID-19 reality or the crisis of liberal democracy versus extreme nationalism and protectionism.

The book contains quite "heavy" quotes and statements that require time and effort to properly understand all the relations and implications, especially for those who are not insiders. It is definitely a very relevant reminder in today's world.

As Keynes observed, there cannot be "liquidity" for the community as a whole. The mistake lies in thinking that markets have a duty to remain liquid or that buyers will always be present to accommodate sellers. The real culprit in 1994 was leverage. If a firm is not in debt, it cannot go broke and cannot be forced to sell, in which case "liquidity" is irrelevant. However, a leveraged firm may be compelled to sell to avoid fast-accumulating losses that could put it out of business. Leverage always gives rise to this same brutal dynamic, and its dangers cannot be emphasized enough.

As Peter Bernstein has written, nature's pattern emerges only from the chaotic disorder of many random events.

After taking Merton's finance course, Kapor decided that quantitative finance was more of a faith than a science - a doctrine for ideologues "blinded by the power of the model." It appealed to intellectuals who craved a sense of order but could lead them disastrously astray if markets moved outside the model.

Merton, however, humbly warned that "it's a wrong perception to believe that you can eliminate risk just because you can measure it."

In the late summer of 1998, the bond-trading crowd was extremely fearful, especially of risky credits. The professors had not modeled this. They had programmed the market for a cold predictability that it had never had; they had forgotten the predatory, acquisitive, and overwhelming protective instincts that govern real-life traders. They had forgotten the human factor.

The second half of When Genius Failed was truly a letdown. I had to exert a great deal of effort to push myself through it. The writing was overly verbose and, frankly, just dull.

On the other hand, the first half was decent enough. I was quite fond of the setup. LTCM was an enormous hedge fund with excellent marketing. It managed to raise a substantial amount of money and achieved huge profits with extremely small margins by taking on a large number of loans. Their investors reaped significant financial rewards. That is, until things took a turn for the worse and everything came crashing down to zero.

In general, I found the story interesting, but I would have preferred a more engaging writing style. The excessive verbosity in the second half really detracted from the overall reading experience. It made it feel like a chore to get through those pages. A more concise and captivating writing approach would have made this book even better.

At the very start of this book, there is a graph that is truly one of the funniest depictions of financial information I've witnessed in quite some time. It is extremely simple - a line illustrating the notional value of a dollar invested in Long-Term Capital Management during the firm's all-too-short existence. The line ascends gradually from its inception in March 1994, gains momentum over the intervening years, reaches a peak of a little over $4 in April 1998, and then plummets Wile E. Coyote-style to approximately 25 cents in the month of August of the same year. You can almost envision hedge fund managers leaping out of their windows.

Lowenstein's account of how this particular group of self-proclaimed geniuses (including not just one but two Economics Nobel laureates) met the depressingly inevitable fate that befalls every other group of smarter-than-the-market Masters of the Universe is both well-written and informative. However, it does become somewhat sluggish towards the end when you read page after page of bankers debating whether to bail out the firm or let it fail. His writing style is smooth, not as flashy or hero-worshipping as Michael Lewis. Although I wish he had delved a little deeper into the math behind their trading strategies, solely for the nerd value, one can only expect so much from a popular work.

One aspect that truly stood out to me is the number of names in the book that could have been directly lifted from the headlines of the subprime crisis a decade after the book was set - Sandy Weill, Robert Rubin, Jon Corzine, Gary Gensler, and so on. Finance is an unusually small world, and one of the many ironies in this book is how reliant the principals of LTCM became on the assumption of personal goodwill between them and the banks they were seeking a bailout from, considering how impersonal and arrogant they were when they were at the top. Despite Lowenstein's efforts to humanize them, they come across like every other hedge fund jerk you've read about, as exemplified in one particularly nauseating exchange.

The Merrill team was impressed with the arbitrageurs, who golfed with as much élan as they traded. Daniel Napoli, Merrill's risk manager, quipped, "If they could have earned a Ph.D at golf, they would have." Stephen Bellotti, who ran foreign currency trading at Merrill, turned to Myron Scholes at one of these weekends and playfully demanded, "Myron, what do you have more of - money or brains?" Scholes shot back: "Brains, but it's getting close!"

But the story of LTCM is unusually significant for several reasons. Firstly, due to the number of people who played major roles in the current financial crisis. Secondly, because of the large precedent set by the firm's too-big-to-fail status. And thirdly, because of the completely nonexistent role played by regulators. The specific details of their trading strategies - highly leveraged arbitrage trades and bets on the convergence of bond yields - are not as crucial as their ignorance of tail risk, as Nassim Taleb has made a career out of discussing, and their willingness to mindlessly leverage themselves to the extreme. Some of the very same banks sitting around the New York Fed conference tables pondering how much to extract from the floundering firm would be back a decade later pleading for their own survival. It is worth considering how this incestuous network of moderately intelligent individuals gets to hold so much power over the broader economy, and how even half-measures to prevent these crises, like Dodd-Frank, are denounced as socialist.

It is an article of faith that macro stability in a market or in an ecosystem requires micro instability. Repeated small fires in an area are healthy and restorative, while artificially suppressing them merely ensures that when fires do occur, they are far more destructive. Similarly, for a financial system to be healthy, there cannot be any such thing as a too-big-to-fail bank or firm, lest the entire network collapses under moments of great stress. In much the same way as the risks LTCM was speculating on were not the uncorrelated random-walk events their Black-Scholes models assumed, the actions of the people who destroyed billions in value were not uncorrelated precisely because they either studied together or were literally the same people who had made similar judgments before. The kind of anti-social behavior that Lowenstein recounts here, even the seemingly harmless kind of dickish condescension of one banker to another, has real consequences for people. And you won't be at all surprised to learn that barely a year after having to grovel before his rescuers, CEO John Meriwether was back in the game with an identical prospectus for the next round of suckers. That old Donald Trump line about how if you owe the bank $10,000 it's your problem but if you owe $10 billion it's their problem is funny when it's just between Trump and his bankers, but not so much when it becomes the taxpayer's problem.

One final amusing quote about risk and uncertainty:

The problem with the math is that it adorned with certitude events that were inherently uncertain. "You take Monica Lewinsky, who walks into Clinton's office with a pizza. You have no idea where that's going to go," Conseco's Max Bublitz, who had declined to invest in Long-Term noted. "Yet if you apply math to it, you come up with a thirty-eight percent chance she's going to go down on him. It looks great, but it's all a guess."

Lowenstein masterfully constructs an excellent narrative centered around the failure of the enormous hedge fund, Long Term Capital Management. The details regarding this failure are intricate, yet I continuously found myself coming back to the fact that numerous factors that were later cited as contributing to the near-collapse of the financial system in 2008 were already clearly present ten years earlier with the downfall of LTMC.

These factors include unregulated shadow banks, the spiraling complexity of derivatives that very few people understood, an over-reliance upon computer models that failed to take into account the fact that people often behave irrationally, the use of massive leverage to magnify returns and make even mild downturns disastrous for investors, and the absolute madness of Alan Greenspan's free market radicalism and his outright refusal to regulate markets.

This book ought to be compulsory reading for anyone who is interested in delving into the true origins of the financial crisis of 2008 and its agonizing aftermath. It is written in a captivating and accessible style that should attract readers who are not familiar with financial jargon.

I'll walk away from this book having learned about a company and a crisis I was rather ignorant of beforehand.

It truly provided a wealth of knowledge. The author did a great job breaking down the technicality of the subject matter. However, I do wish it had incorporated more pictures or graphics to enhance the understanding further.

The book also excelled in characterizing and motivating the major players. It brought them to life and made their actions and decisions more understandable.

Nevertheless, towards the end, it became a struggle as the sheer volume of names caused everyone to blur together. It would have been beneficial if there was a better way to distinguish between them.

Moreover, I really wish the book had an updated epilogue for where the key players are 20 years later. This would have added a fascinating dimension to the story and given readers a better sense of the long-term impact. Overall, it was an informative and engaging read that left me with a newfound understanding of the company and the crisis.

This book was rated a four.

And then came the epilogue. Roger Lowenstein did an excellent job in summarizing what was a colossal collapse by Long Term Capital Management. The epilogue truly emphasized the point. It makes one wonder why, having graduated from college just last May, finance majors are repeatedly taught the efficient market theory, yet they never hear about behavioral finance until they read books like this. How many times do we need to be shown that markets are simply not rational before we finally take the hint?

I found it extremely fascinating that LTCM was such a large firm that when the news broke that it was in trouble, other banks hastily rushed to sell their positions. They knew that if LTCM had to liquidate, the markets would crash simply because LTCM's positions were so enormous.

I highly recommend this book to anyone with an interest in business and finance. The boldness of LTCM's management was not what surprised me the most. It was the fact that almost the exact same scenario - this time in CMBS instead of bonds and currencies - repeated itself less than ten years later in the crash of 2008.

When Genius Failed presents a captivating narrative about the ascent and descent of Long-Term Capital Management (LTCM). The book commences by meticulously outlining the hedge fund's establishment and its astonishing success. This success was propelled by innovative trading tactics that yielded billions of dollars for its founders and shareholders. Nevertheless, the tale culminates with LTCM's spectacular downfall. This was a consequence of market manipulation, geopolitical unrest, and a harsh bear market, which left the fund teetering on the verge of bankruptcy, with its founders forfeiting over 90% of their net worth.

The book offers invaluable lessons for investors, highlighting the perils of excessive leverage, the risks linked to overconfidence, and the snares of depending on past performance to forecast future market circumstances.

While reading this book, one cannot refrain from questioning the genuine societal worth of this kind of investing. It is disconcerting to witness some of the most brilliant minds devoting their talents to accumulating enormous personal wealth through algorithmic trading, arbitrage, and financial engineering - strategies that generate wealth without producing anything tangible or contributing to the wider economy.

LCTM was a hedge fund led by John Meriwether, who had previously led a bond trading group at Salomon. He was joined by his two top traders, Haghani and Hilibrand. The group also included Harvard professors, a former VP of the Fed, and two Nobel Prize laureates, Scholes and Merton. Almost all of these individuals had MIT PhDs.

From what I understood, they used their influence to raise capital and obtain large amounts of leverage. They utilized their expertise to develop models that generally indicated the market was overpaying for reduced risk, and they bet on the market eventually pricing them correctly according to their models. However, for a couple of months, the markets moved in the opposite direction of what their models predicted, and they lost 4 billion dollars.

My impression is that the Nobel Prize-winning duo and the academics were relatively hands-off, similar to a PhD advisor. Most of the decisions were made by Haghani and Hilibrand. The professors' largest contribution was in acquiring leverage.

One question I have is whether their models ever indicated that people were underpaying for risk on a particular security. This seems like an actual "hedge" against the market "irrationally" overpricing risk. If trading according to the models had similar success and failure modes as "picking the similar, riskier security," what was the point of the models?

The partners' assertion that they were conspired against and that the models were right and it was an incredible fluke "10 sigma event" is delusional. If you believe in p-values, when a 10 sigma event occurs, you reject your null hypothesis that a 10 sigma event did not happen. Also, being conspired against and losing does not mean you are right and the game is wrong; you are just wrong.

Overall, this book is a complete bore. There are too many people, and it's difficult to keep track of them all. The technical material is presented at a level that is beyond my comprehension. The evolution of the acquisition is incredibly dull, and I didn't care about it at all.

The book is too much like journalism, missing the forest for the trees. It is not accessible to a general audience, and some better explanations could have improved the situation. I'm not going to remember the names of the characters; please give them some distinguishing traits. Basically, I'm spoiled by Michael Lewis books.

Most of the ideas in "The Black Swan" are scattered throughout this book.

Some quotes:

"You're picking up nickels in front of bulldozers."

"Long-Term envisioned markets as stable systems in which prices moved about a central point of rational equilibrium. 'I had a different view,' Soros noted. The speculator saw markets as organic and unpredictable. He felt they interacted with, and were reflective of, ongoing events. They were hardly sterile of abstract systems. As he explained it, 'The idea that you have a bell-shape curve is false. You have outlying phenomena that you can't anticipate on the basis of previous experience.'"

"... a couple of other attorneys were trying to tell Hilibrand what it meant, but he didn't want to listen, he wanted to read it himself, and he could barely see it through the tears that were streaming down his face. He didn't want to sign, he wailed... Hilibrand, who had never needed anyone and who had once rebelled at paying for his share of the company cafeteria but now couldn't pay his debts, refused. Then Allison talked to him and said they were trying to restore the public's faith in the system and not to destroy anybody, and J.M. said, 'Larry, you better listen to Herb.' And Hilibrand signed, and the fund was taken over by fourteen banks."

Lowenstein undertakes a workmanlike task of constructing a lucid narrative and expounding on the technical particulars of the financial markets. The entire trajectory of the rise and subsequent fall of Long Term Capital Management is presented clearly from start to finish. Although the story doesn't reach soaring heights, it never drags or gets mired in minutiae. Overall, I not only relished the book but also gleaned some knowledge. As an outsider to the hedge fund realm, I valued Lowenstein's frequent pauses to elucidate a specific trade or strategy. Moreover, I liked his numerous analogies and examples that translated the deals into straightforward English for the layperson. It is all executed very well.

However, since Lowenstein had almost no access to the key figures at Long Term Capital Management, the storytelling feels somewhat detached from the actual action. For example, there is scarcely any dialogue throughout the book. Having the characters speak, argue, and interact under intense pressure would have added drama and a sense of being in the midst of the action. It would be wonderful to experience the tension and directly sense the confidence and yes, arrogance of the various players. Of course, given the limitations imposed on Lowenstein's research and reporting, adding dialogue would transform the story into fiction, which would render this an entirely different (and not as useful) book. Here, accurate nonfiction prevails over recreated drama, as it should.

If you have an interest in the high-risk/high-reward world of investing, and if you desire yet another account of the markets on the verge of disaster (and if you enjoy seeing the overly proud humbled), When Genius Failed is undoubtedly worth a perusal.