Posts Tagged ‘Oak Ridge’

Meditations

The price of the Manhattan Project

Friday, May 17th, 2013

There's been a little radio silence over here last week; the truth is, I've been very absorbed in NUKEMAP-related work. It is going very well; I've found some things that I thought were going to be difficult to be not so difficult, after all, and I've found myself to be more mathematically capable than I usually would presume, once I really started drilling down in technical minutiae. The only down-side of the work is that it is mostly coding, mostly technical, not terribly conducive to having deep or original historical thoughts, and, of course, I've gotten completely obsessed with it. But I'm almost over the hump of the hard stuff.

Two weeks ago, I made a trip out to the West Coast to hang out with the various wonks that congregate at the Center for Nonproliferation Studies at the Monterey Institute for International Studies. This was at the behest of Stephen Schwartz, who teaches a class over there and had me come out to talk to them about nuclear secrecy, and to give a general colloquium talk.

Atomic Audit

Stephen became known to me early on in my interest in nuclear things for his work in editing the book Atomic Audit: The Costs and Consequences of U.S. Nuclear Weapons Since 1940 (Brookings Institute, 1998). This is one of these all-time useful reference books; it is the only book I've read, for example, that has anything like a good description of the development of US nuclear secrecy policies. And the list of contributors is a who's-who of late 1990s nuclear scholarship. The book includes really detailed discussions about how difficult it is to put a price tag on nuclear weapons spending in the United States, for reasons relating both to the obvious secrecy issue, but also the fact that these expenses have not really been disentangled from a lot of other spending.

I've had a copy of the book for over a decade now, and it has come in handy again and again. I'm not a numbers-guy (NUKEMAP work being the exception), but looking at these kind of aggregate figures helps me wrap my head around the "big picture" of something like, say, the Manhattan Project, in a way that is often lost by the standard historical approach of tight biographical narratives. Of the $2 billion spent on the Manhattan Project, where did it go, and what does it tell us about how we should talk about the history of the bomb?

Here is a breakdown of cost expenditures for the Manhattan Project sites, through the end of 1945:

Site/Project 1945 dollars 2012 dollars %
OAK RIDGE (Total) $1,188,352,000 $18,900,000,000 63%
K-25 Gaseous Diffusion Plant $512,166,000 $8,150,000,000 27%
Y-12 Electromagnetic Plant $477,631,000 $7,600,000,000 25%
Clinton Engineer Works, HQ and central utilities $155,951,000 $2,480,000,000 8%
Clinton Laboratories $26,932,000 $430,000,000 1%
S-50 Thermal Diffusion Plant $15,672,000 $250,000,000 1%
HANFORD ENGINEER WORKS $390,124,000 $6,200,000,000 21%
SPECIAL OPERATING MATERIALS $103,369,000 $1,640,000,000 5%
LOS ALAMOS PROJECT $74,055,000 $1,180,000,000 4%
RESEARCH AND DEVELOPMENT $69,681,000 $1,110,000,000 4%
GOVERNMENT OVERHEAD $37,255,000 $590,000,000 2%
HEAVY WATER PLANTS $26,768,000 $430,000,000 1%
Grand Total $1,889,604,000 $30,060,000,000

I've taken this chart from here. The "current dollars" are 2012 dollars, with a "production line" labor deflator used (out of all of the options here, it seemed like the most appropriate to the kind of work we're talking about, most of which was construction).

To break the numbers down a bit more, K-25, Y-12, and S-50 were all uranium enrichment plants. Hanford was for plutonium production. "Special operating materials" refers to the raw materials necessary for the entire project, most of which was uranium, but also highly-refined graphite and fluorine, among other things. Los Alamos was of course the design laboratory. The heavy water plants were constructed in Trail, British Columbia, Morgantown, West Virginia, Montgomery, Alabama, and Dana, Indiana. Their product was not used on a large scale during the war; it was produced as a back-up in case graphite proved to be a bad moderator for the Hanford reactors.

I'm a visual guy, so I of course immediately start looking at these numbers like this:

Manhattan Project costs chart

Which puts things a little more into proportion. The main take-away of these numbers for me is to be pretty impressed by the fact that some 80% of the money was spent on the plants necessary producing fissile materials. Only 4% went towards Los Alamos. And yet, in terms of how we talk about nuclear weapons and the Manhattan Project, we spend a huge amount of the time talking about the work at Los Alamos, often with only token gestures to the work at Hanford and Oak Ridge as the "next step" after the theory had been worked out.

We can also break those numbers down a little finer, by turning to another source, Appendix 2 of Richard Hewlett and Roland Anderson's The New World. There, they have costs divided into "plant" and "operations" costs:

Site/Project Plant Operations Plant %
OAK RIDGE (Total) $882,678,000 $305,674,000 74%
K-25 Gaseous Diffusion Plant $458,316,000 $53,850,000 89%
Y-12 Electromagnetic Plant $300,625,000 $177,006,000 63%
Clinton Engineer Works, HQ and central utilities $101,193,000 $54,758,000 65%
Clinton Laboratories $11,939,000 $14,993,000 44%
S-50 Thermal Diffusion Plant $10,605,000 $5,067,000 68%
HANFORD ENGINEER WORKS $339,678,000 $50,446,000 87%
SPECIAL OPERATING MATERIALS $20,810,000 $82,559,000 20%
LOS ALAMOS PROJECT $37,176,000 $36,879,000 50%
RESEARCH AND DEVELOPMENT $63,323,000 $6,358,000 91%
GOVERNMENT OVERHEAD $22,567,000 $14,688,000 61%
HEAVY WATER PLANTS $15,801,000 $10,967,000 59%
Grand Total $1,382,033,000 $507,571,000 73%

They do not define how they differentiated between "plant" and "operations" expenses, but the most plausible guess is that the former are various start-up costs (e.g. construction) and one-off costs (e.g. big purchases of materials) and the latter are day-to-day costs (general labor force, electricity, etc.).

Looking at that percentage can tell you a bit about how much of the Manhattan Project was the building of a weapons production system as opposed to building three individual weapons. Nearly three-fourths of the expense was for building a system so large that Niels Bohr famously called it country-sized factory.1

The K-25 gaseous diffusion plant: the single largest and most expensive Manhattan Project site.

The K-25 gaseous diffusion plant: the single largest and most expensive Manhattan Project site.

Another way to look at this is to say that we usually talk about the atomic bomb as project focused on scientific research. But one could arguably say that it was more a project of industrial production instead. This is actually quite in line with how General Groves, and even J. Robert Oppenheimer, saw the problem of nuclear weapons. Oppenheimer, in testimony before Congress in 1945, went so far as to phrase it this way:

I think it is important to emphasize [the role of industry in the Manhattan Project], because I deplore the tendency of myself and my colleagues to pretend that with our own hands we actually did this job. We had something to do with it. If it had not been for scientists, there would have been no atomic bomb; but if there had been only scientists, there also would be no atomic bomb.

This is actually a very important point, and one which shines light onto a lot of other questions regarding nuclear weapons. For example, one of the questions that people ask me again and again is how close the Germans were to getting an atomic bomb. The answer is, more or less, not very close at all. Why not? Because even if their scientific understanding was not too far away — which it was not, even though they were wrong about several things and behind on several others — they never came close to the stage that would be necessary to turn it into an industrial production program, as opposed to just a laboratory understanding. That sheer fact is much more important than whether Heisenberg fully understood the nature of chain reactions or anything like that.

Why do we think of the bomb as a scientific problem as opposed to an industrial one? There are perhaps a few answers to this. One is that from the beginning, the bomb came to symbolize the ultimate fruits of scientific modernity: it was seen as the worst culmination of all of those centuries of rational thought. What grim irony, and what a standard story, that knowledge could lead to such ruin? Another reason is that scientific adventure stories are more interesting than industrial adventure stories. It is much more fun to talk about characters like Szilard, Oppenheimer, and Feynman running around trying to solve difficult logic problems in a desperate race against time, than it is to talk about the difficulties inherent to the construction of very large buildings.

Finally, though, there is the issue of secrecy. The scientific facts of the atomic bomb, especially the physics, were the most easily declassifiable. As discussed in a previous post (with many nods towards the work of Rebecca Press Schwartz), one of the main reasons the Smyth Report was so physics-heavy is because the physics was not terribly secret. Nuclear chain reactions, the idea of critical mass, the basic ideas behind uranium enrichment and reactors: all of these things were knowable and even known by physicists all over the world well prior to the bombing of Hiroshima and Nagasaki. The really hard stuff — the chemistry, the metallurgy, the engineering "know-how," the specific constructions of the massive fissile-material production plants — was silently omitted from official accounts.

Looking at the costs of the bomb help rectify this perception a bit. It still doesn't get us outside of the heroic narratives, for they are very appealing, but it can help us appreciate the magnitude of what is left out of the standard story.

Notes
  1. Bohr reportedly told Teller upon seeing Los Alamos and hearing about the entire project: "You see, I told you it couldn't be done without turning the whole country into a factory. You have done just that." []
Meditations | News and Notes

Three losses

Friday, January 25th, 2013

There were three Manhattan Project losses that I heard about over the last week that I thought were worth briefly commenting on. They highlight, in different ways, how the living history of the Manhattan Project is rapidly vanishing.

Erwin Hiebert, 1972. From the Radcliffe Archives.

Erwin Hiebert, 1972. From the Radcliffe Archives.

Erwin Hiebert had worked as a chemist at the Chicago Metallurgical Laboratory. He passed away last November, though a notice was just recently sent around. I interviewed him a few years back, though not about his bomb work (connected with doing some local Harvard history). I believe I recall him telling me he had worked with Harold Urey on diffusion research. He later became an historian of science, and this was the capacity I knew him in. He was a charming old man, very helpful, very friendly. He wasn't a major figure on the Manhattan Project, but it's sometimes worth remembering how many people were involved in the project other than the main, well-known scientists and the thousands of construction workers or miscellaneous technicians. I recently had a chance to look up just how many people working at the Met Lab — we normally only hear about the 20 or so people who worked on the pile, but at its height, there were around 2,000 people working at Chicago on the bomb, with some 750 of them doing it in a scientific (as opposed to administrative or construction) capacity.

Assembling the Trinity device: Louis Slotin, Herb Lehr, and — I believe, at top right — Donald F. Hornig. It looks a lot like him, to me.

Assembling the Trinity "Gadget": Louis Slotin, Herb Lehr, and — I believe, at top right — Donald F. Hornig (magnified). It looks a lot like him, to me, but I don't have confirmation of this. The "Gadget" is at far left, of course; on top of the box next to it is the container with its plutonium core.

Donald F. Hornig also recently passed away. He worked at Los Alamos during the war, and was heavily involved in the instrumentation work that was required for the implosion bomb. He was credited as the inventor of the triggered spark-gap switch (a "low-impedance switch"), which was the switch necessary to divert a high-voltage signal to the 32 detonators on the "Gadget" with a simultaneity tolerance of only nanoseconds. (A patent application for this switch had been filed in his name in late 1945; it was declassified and granted in 1976. Hornig told me he had no awareness of it being filed or granted when I talked to him a few years back.) He was also one of the last people in the "Trinity" tower before its detonation, checking the electrical connections, which proved to be a somewhat hair-raising experience. He describes his work at "Trinity" in some detail here. It's worth a read:

I think I was the last person down from the tower although there might be a little bit of argument about that. I won't go into any detail, but Oppenheimer had gotten worried about nine o'clock the night before about how easy the thing was to sabotage by anyone who really knew anything about it, and so I believe it was Kistiakowsky, Bainbridge and I who each took a turn sitting with it up on the tower. My turn came from around nine o'clock until midnight, in the midst of a violent thunder and lightning storm. You get philosophical in those circumstances. You know, either you do get hit by lightning or you don't and either way you won't know what happens.

He had many later achievements, including being LBJ's science advisor.

The Oak Ridge K-25 plant in 1945.

The Oak Ridge K-25 plant in 1945.

Lastly, the K-25 plant has been completely destroyed. The Oak Ridge facility, which had been used during and after World War II to enrich uranium via the gaseous diffusion method, was the largest factory under one roof at the time it was constructed. It had been long since shut down, and, a few years back, all but one "cell" of its building had been destroyed. A number of people had been trying to keep the cell preserved as an historic site, but it came to naught. It took only 20 minutes to permanently knock down the last piece of it, the last indication of the scale of this site.

I think this is really too bad — a completely missed opportunity. I know that there are people who have mixed feelings about preserving the Manhattan Project sites — they think that they will be used as excuses to glorify the atomic bomb. I think this is entirely misguided. These sites are ambiguous and they provoke different reactions from different people. By analogy, there can be controversy over how the Enola Gay should be presented to the public, but the answer is not to melt the Enola Gay into scrap. Destroying these sorts of legacies is a permanent act, whereas the act of interpretation is an always changing one. Erasing history is not the right response to the fact that we still disagree over it. Destroying the sites where the atomic bomb was made will not change the fact that we made the atomic bomb.

The last generation of people who worked on the first atomic bombs is passing away. The bomb still exists. We should be doing more to preserve these sites, even if they make us uncomfortable, even if we are unsure how they will be used by people in the present or the future.

Meditations

Cold War Sex, Cold War Secrecy

Monday, April 30th, 2012

This weekend I read a fascinating article in the New York Times about the unusual death of an MI6 agent. The agent in question was found dead in his apartment, badly decomposed and locked in a duffel bag. Apparently the "official" line here is that he was into unusual sexual games, including "claustrophilia," a fetish so outre that even the venerable Wikipedia doesn't yet have an entry on it in its copious library of paraphilias.

"Photographs from a video show an expert trying to determine whether Mr. Williams could have locked himself in a duffel bag." I don't judge. (Reuters via The New York Times)

That's titillating, I suppose, but what's really interesting here is that the UK intelligence agencies are using this as an example of the fact that they don't care about the outre sexual practices of their agents anymore — and because of that, it isn't blackmail material. That's a pretty bold thing to say, given the sordid history of intelligence agencies in prosecuting homosexuals and others who engaged in other-than-heteronormative sexual activity during the Cold War. (On this, see David K. Johnston's The Lavender Scare.)

The official line here was that "sex deviants" were probably psychologically unwell (this is, of course, the period in which homosexuality was still classified as mental illness), and, even if they weren't, that they were vulnerable to blackmail attempts, and thus could be vulnerable to being coerced into aiding enemy powers. Or putting that last part in its fully circuitous form: because homosexuals were not tolerated, they were vulnerable to blackmail, thus they could not be tolerated. 

The U.S. Atomic Energy Commission was no stranger to these Cold War concerns. In February 1951, just before the beginning of the Rosenberg trial, AEC Chairman Gordon Dean reported to the Joint Committee on Atomic Energy that they had rooted out a high-placed homosexual:1

  • Mr. Dean: ... We had one other pleasant thing during the course of the last month. We found out that a man down at Oak Ridge, who was in charge of personnel, was given to homosexual activity. He was arrested up here in the District of Columbia when he was up here on a trip; and of course we removed him from the payroll immediately, fired him.
  • We have also checked to see if there has been anybody brought into the program by him who might be a person with similar proclivities at the Oak Ridge office. We see no evidence of that at this point.
  • Mr. Holifield: How long had he been personnel officer at that point?
  • Mr. Dean: A matter of three years, I think. [...]
  • Sen. Bricker: What did he do?
  • Mr. Dean: He was a homosexual, picked up here by the police in Washington, D.C. It was a very unfortunate place for a man to be in, a place as high in the program as the personnel office of Oak Ridge, but such things happen.
  • Sen. Hickenlooper: He failed to report a former arrest on his PSQ [Personnel Security Questionnaire, required for security clearances], didn't he?
  • Mr. Dean: In looking back in the file we find he did not report an arrest in his PSQ. At a subsequent hearing, which took place about two and a half years ago, he was interrogated about this, and the interrogation was not skillfully conducted and they got almost up to the point of why he had been arrested and what it was all about and then it trails off into the transcript. [...]
  • Mr. Cole: What is the reason your folks weren't able to discover his weaknesses in the three years he was down there?
  • Mr. Dean: He is perfectly normal apparently when he is down there. He is a married man, he engaged in sexual intercourse. When he goes out of town, apparently this other thing comes on him. He got liquored up. It is when he drinks excessively. There is no indication from anybody down there he was even suspected of this sort of activity. [...]
  • Sen. Bricker: Was there any evidence in this man's contacts and associations away from there that there was any security risk?
  • Mr. Dean: No. [...]
  • Sen. Bricker: I mean, in his homosexual activities outside. Do you know of any pressure that might be used against him to give secrets and to get any more of his kind into the operation?
  • Mr. Dean: Is there evidence of that?
  • Mr. Waters: No evidence of that.

What a sad thing. Here's a guy who has spent the one life he has living in a horrible closet — not just one mandated by the social norms, but the "national security" requirements of his career. He's so deep in the closet, so afraid, that he doesn't act upon it unless out of town and very drunk. He gets arrested for his sexual preferences, loses his job, god knows what else. At least he was probably unaware that his sexual habits were being discussed (in secret) by one of the most powerful Congressional committees of all time.

I think it's actually a great thing that MI6 has made a point of explicitly breaking the original circuitous cycle. If they don't care about the sexuality of their agents, then it isn't blackmailable, and thus they don't have to care.

A few weeks ago I had the pleasure of getting acquainted with Avner Cohen, author of Israel and the Bomb and The Worst-Kept Secret, the books on the history of the Israeli nuclear program. He shared with me a quote from Mordechai Vanunu's lawyer, Avigdor Feldman, that I've been coming back to a lot lately:

"If something is secret, and something else touches it, it too becomes secret. Secrecy becomes a disease. Everything around the secret issue becomes secret, so the trial became a secret, so I became a secret."

Secrecy, as Avner puts it, is contagious. It spreads. It goes from something that we might all agree ought to be secret — how to make a weapon of mass destruction, to take the canonical example. But from that point of apparent agreement, it seeps out, worming its way into the lives of everyone who comes near it — even into the bedroom, that most private of places.

Notes
  1. Executive Session CCLXXXVIII (8 February 1951), Joint Committee on Atomic Energy. []
Redactions

General Groves Meets the Press (1945)

Wednesday, April 18th, 2012

Since I’ve already been engaged in some Oak Ridgery earlier in the week, I thought I might continue the trend. This week’s document is the transcript of a press conference given by Secretary of War Robert P. Patterson and General Leslie R. Groves at Oak Ridge on September 29, 1945.1

It’s one of the few press conferences that Groves gave during this time, one of the few times early on in which he actually made personal appearances with the press, as opposed to his more carefully-constructed, only-by-paper publicity campaigns.2

Click to view document (sorry about the poor resolution — blame NARA and their low-res online versions)

It’s a fascinating exchange between the press and the deacons of secrecy, at the secret city itself.

Question: "What is the Army's position on the release of the secret?"
Patterson: "I am not in a position to say that. A decision as to policy is to be made by the President and is to be made very shortly and I prefer not to say anything about that, but you won't have to wait long."

You won't have to wait long. One wonders what this refers to. Truman did issue various requests for the secret to be "kept" around about this time, as a temporary measure. The Attlee-Truman-King statement was issued in November, which had a very ambiguous take on the question of secrecy (see section 6 in particular, which suggests short-term secrecy is important, but that long-term secrecy is ineffective), and then there is the entire Baruch plan debacle.

Question: "How many people actually knew what you were doing?"
Patterson: "I don't think anyone could answer that question."
Question: "Less than 100?"
Patterson: "I would say more than that but that would be pure speculation."

"Actually knew what you were doing" refers, presumably, to the fact that the end goal was making an atomic bomb. It's quite a bit more than 100 (if you include, for example, the weapons designers at Los Alamos), but it's an interesting list to consider. I've played with creating a table of "who knew" myself; it has some interesting parts of it (Vice President Harry Truman: did not know. Soviet Premier Josef Stalin: did know. Most workers at Oak Ridge and Hanford: did not know. Most members of Congress: did not know.) but  never quite did enough to justify an entire table.

Question: "Is there anything to the rumor that you are making a super bomb that would make the Nagasaki bomb look small?"
Patterson: "I don't know."
Groves: "I don't think the Nagasaki bomb was made obsolete. That bomb could never be made obsolete. Those we used are pretty super." [last sentence hand-written] ...
Question: "Is there such a thing being planned as a super bomb?"
Groves: "No, I don't think so. They talk about airplanes that will go around the world, etcetera. This thing has just started and no one knows just what will develop."

This is, as far as I know, the first published reference to a rumor of a possible "Super" bomb, the hydrogen bomb, in the public domain -- as early as September 1945! Note how sneaky Groves is in the first instance. He doesn't deny anything, he doesn't confirm anything. He's evasive but in a way that doesn't actually give anything away. He's right, of course, that no matter how you slice it, 20 kilotons is going to be a pretty big bang. His second statement is more dishonest; he knew that there was a "Super" bomb being contemplated.

Click to continue: Groves gets asked about radioactivity at Hiroshima...

Notes
  1. The photo of Groves is actually from Hanford; I couldn't find any of him giving talks at Oak Ridge. Photo is from the Hanford DDRS database, item N1D0029056. []
  2. Transcript, "Press Conference — Secretary of War Robert P. Patterson — Clinton Engineer Works," (29 September 1945), National Archives and Records Administration, available online through their ARC website under the identifier 281581. []
Meditations

Oak Ridge Confidential, or Baseball for Bombs

Monday, April 16th, 2012

Oak Ridge, Tennessee, has the dubious honor of having been one of the few places in the United States that qualified for the label of "secret city." What we usually have in this country are secret sites, but Oak Ridge was more than a site. During World War II, Oak Ridge had a population of 75,000 people, making it the fifth largest city in the state — one that didn't appear on official maps.

The Department of Energy has recently been digitizing a large number of photographs of life at Oak Ridge, and it seemed like a good time to talk about the place. I would be remiss not to send interested readers to Frank Munger's Atomic City Underground, which is a site that lives and breathes Oak Ridgery seven days a week. Some of my favorites from the new photos:

Oak Ridge was big for a secret city. Even the presence of "secret cities" or secret sites on a massive scale were pretty novel for the United States at the time. The only pre-World War II analog that I've come across is the lewisite (chemical gas) production facility during World War I known as "the Mousetrap" (once you enter, you never leave), where James B. Conant (future atomic administrator) worked as a young chemist.1

Most of the personnel at Oak Ridge were in construction of some sort. It's easy to see why, when you look at what they made there. The job of producing fissile material (enriching uranium, in this case) was mostly a construction job. No shock, then, that it was the Army Corps of Engineers who were called in to run the project in 1942, and that the guy they chose to head the whole project (Gen. Leslie Groves) had recently constructed the Pentagon -- still the world's largest office building by area. I like to point out to students that all of the world's nuclear fission research in 1938 could fit onto an average-sized dinner table; in less than a decade, it spanned an entire country.

The K-25 gaseous diffusion plant, at the time the largest single factory under one roof in the entire world.

The level of secrecy and compartmentalization at Oak Ridge created a number of practical problems for those running the site. It wasn't just that Oak Ridge was cut off from the outside world, which it was. It was also cut off from the rest of the Manhattan Project, kept under tight compartmentalization restrictions.

The vast majority of those working at Oak Ridge during the war had no idea what they were working on. They knew it involved building very large facilities, that there were various health hazards involved, and that supposedly it was an important war project. All of those who were there thought they had signed up to do their part, yet the war in Europe seemed to end without any intervention on their part.

The National Archives has a great transcript of a radio show from 1947 that sheds a lot of interesting light on what it was like for your average technician to work at Oak Ridge. Here's a quote from George Turner, who apparently managed workers:

Well it wasn't that the job was tough... it was confusing. You see, now one knew what was being made in Oak Ridge, not even me, and a lot of the people thought they were wasting their time here. It was up to me to explain to the dissatisfied workers that they were doing a very important job. When they asked me what, I 'd have to tell them it was a secret. But I almost went crazy myself trying to figure out what was going on. One man came up to me and said, "I thought this was a war job." "It is," I said. He looked at me very unbelieving. "Well I've been here two months now," he stated, "And I've been watching those two smoke stacks outside every day, and no smoke has ever come out of them... There's something funny going on around here and I'm getting out."

The smoke stacks, it goes on to explain, were intake stacks, pulling fresh air in to the plant. It also describes how the railroad cars full of freight -- uranium -- always left empty, another suspicious looking thing.

Rumors abounded about what the plant was meant to accomplish, both inside and outside of it. These rumors were, of course, carefully cataloged by Manhattan Project security officials. The most amusing one I've come across for Oak Ridge was that it was actually a model socialist community being created by Eleanor Roosevelt as a prototype for future Communist domination of the United States. Nothing encourages nonsense like a vacuum of information.

More compartmentalization stories follow, along with the unusual solution proposed by Manhattan Project administrators...

Notes
  1. This period of Conant's life is covered wonderfully in James Hershberg's James B. Conant: Harvard to Hiroshima and the Making of the Nuclear Age (New York: Knopf, 1993), chapter 3. []