Critique of Evan
Harris Walker’s Letter in Physics Today,
February 1991
by Allen Esterson
In the February 1991 issue of Physics Today Evan Harris Walker responded to a letter published by
John Stachel in reply to one by Walker
in the February 1989 issue of Physics
Today. What follows is a critical examination of Walker’s February 1991 letter, taken point by
point.[1]
John Stachel stated in his February 1989 letter to Physics Today that, aside from one
comment on a course she took, “none of Marić’s
letters to Einstein touches on any substantive point in physics, while his to
her are chock-full of substantive comments on books and articles in physics…”
and that “one could not select ten of Einstein’s letters to Marić that would be as devoid of references to physics as
are hers to him”. Walker
retorts that in this “Stachel is wrong. Eleven of Einstein’s letters to Mileva
have no reference to science at all…” Now while there is no doubt that Stachel
was over-hasty in his statement, three of the eleven letters cited by Walker do in fact have a
brief reference to physics. (Documents 40 and 41 refer to a volume by the
physicist Paul Drude that Einstein is reading,[2]
and document 68 has a passing reference to a book by the physicist Rudolf
Kirchhoff.)[3]
Nevertheless, Walker is correct insofar as that more than ten letters of
Einstein’s have no reference to physics, or only a passing citing of a physics
volume, or allusions to their coursework at Zurich Polytechnic of the kind that
also occurs in some of Marić’s letters to Einstein.
This does not alter the essential picture that Stachel is emphasizing: that in
nearly two-thirds of Einstein’s 43 letters he writes of his ideas on topics
outside the curriculum or refers to books or papers dealing with such topics,
contrasting strongly with the lack of such items in Marić’s letters, which
are dominated by references to personal matters.
Whereas Stachel is right when he
observes that there is nothing in any surviving letter of Marić’s remotely
comparable to the substantive material on his own ideas to be found frequently
in Einstein’s, Walker goes wrong as soon as he starts to infer what was in the
many letters of Marić’s that have not survived. He writes: “To determine
what Marić’s letters likely contained, we must…examine Einstein’s letters
to her. It happens by doing so we can
tell that many of her lost letters make reference to her scientific work, to
her comments on science and to their collaborative efforts. I find statements
in 13 of his 43 letters to her [references given] that refer to her research or
to ongoing collaborative effort – for example, in document 74, ‘another method
which has similarities with yours’.”
This claim is vitiated by the fact
that Walker
fails to distinguish between research undertaken by Marić and Einstein for
their diploma dissertations as part of
their course at the Polytechnic (they both chose topics on heat conduction)
and research on his own ideas of the kind that Einstein often refers to in his
letters. For instance, in document 74 that Walker cites Einstein is referring to
Marić’s diploma dissertation on heat conduction (which she also hoped to
use for her doctoral thesis, discontinued in 1901).[4] This also applies to Walker’s citing
Einstein’s writing “I am also looking forward very much to our new work. You
must now continue with your investigation” in the following letter (document
75). The second sentence continues: “how proud I will be when maybe I’ll have a
little doctor for a sweetheart while I am myself still a totally ordinary man”.
The research in question, as is evident from Einstein’s previous letter,
relates to her dissertation on heat conduction, not to the kind of
extra-curricular ideas that Einstein frequently writes about, which were to
culminate in papers published in the next few years.
The rest of Walker’s case in connection with the
Einstein-Marić correspondence concerns Einstein’s occasional use of
inclusive language (“our” and “we”) in regard to his ongoing extra-curricular
studies. This line of argument has been amply refuted by Stachel,[5] and here I can only make a few
brief points.
Walker does not cite the numerous
occasions that Einstein uses first person singular pronouns (“I” and “my”) with
respect to the very same work in regard
to which he uses first person plural pronouns on one or two occasions. For
instance, later in the year (1901) in which he referred to “our work on
relative motion” he told Marić:
“I’m busily at work on an electrodynamics of moving bodies, which promises
to be quite a capital piece of work.” (At this stage he was still working with
classical (Galilean) relative motion. This was some four years before he wrote
the 1905 paper incorporating his crucial special relativity principle that
eliminated the concept of the ether.) Again, there are letters that Marić
writes to her friend Helene Kaufler in which she unambiguously attributes to
Einstein papers on topics in regard to which he had once or twice used
inclusive language.[6] There are also letters of Marić’s
to Kaufler in which she writes “how proud I am of my darling” in relation to
his first published paper, and of the “real admiration” she has for the first
attempt at a doctoral thesis by Einstein, “who has such a clever head”.[7] These are not the words of a
collaborator in Einstein’s research; they are more in line with the sentiment
expressed by Einstein, writing to Marić in 1901: “Soon you’ll be my
‘student’ again, like in Zurich.”[8]
Walker’s contention that it can be
inferred from Einstein’s letters that the lost letters by Marić contain
reference to her scientific work is only true with regard to her diploma
studies, and more specifically, to their diploma dissertations. There is no
evidence of significant collaboration by Marić in his extra-curricular
writings beyond joint reading of books and occasional help in locating material
when they were students. The comments in Einstein’s letters relating to his
extra-curricular research on physics indicate his need to communicate his
current ideas to an interested listener, and provide no evidence of responses
in kind. (In the two instances where we have letters of Marić’s responding
directly to ones of Einstein’s containing such material, she makes no mention
whatever of the ideas he had written about. In another letter in which Einstein
reports that he has had an idea about a body’s motion relative to the ether, he
adds: “But enough of this! Your poor head is already crammed full of other people’s hobby horses that you’ve
had to ride” [emphasis added].)
As Stachel argues, the inclusive
language used by Einstein at certain times reflects his desire for a joint life
together devoted to physics, whereas the indications that published work was
solely Einstein’s, and the complete absence of any document containing ideas of
Marić’s on physics, are not consistent with the notion of her making any
substantive contribution to his 1905 papers.[9]
Presumably to buttress the notion
that Einstein could not have been capable of his later achievements without the
assistance of Marić, Walker
writes in relation to Einstein’s record at the Zurich Polytechnic: “In 1895
Einstein failed his first try at the entrance examinations for the ETH
[formerly Zurich Polytechnic]. Though Einstein did well in the intermediate
examination in 1898, by 1899 he was having difficulties. In March 1899 he
received the ‘director’s reprimand for nondiligence in physics practicum.’ By
1900 Einstein’s grades were down. Albert passed with a questionable 4.91,
trailing well behind Jakob Ehrat, Marcel Grossman and Louis Kollros, whom he
had previously led.” [Citations omitted]
In this passage Walker tendentiously omits facts that cast a
completely different light on the situation. Prior to Einstein’s first attempt
at the entrance examination for Zurich Polytechnic he had living in Italy (mostly
with his parents) for some nine months without formal schooling. Moreover, he
was only 16 at the time, and as he was about eighteen months below the
stipulated age of 18 he had to obtain special permission to take the exam. He
failed to achieve the required standard in languages and some other subjects,
but his results in mathematics and physics were exceptional. On the advice of
the Principal of the Polytechnic he attended high school in
Aarau in Switzerland
to cover the gaps in his knowledge. His school-leaving certificate the
following year records that he achieved maximum grades in algebra and geometry,
high grades in physics and chemistry and some other subjects, and performed
badly only in French.[10]
When he enrolled at the Polytechnic for the diploma course for teaching
mathematics and physics in October 1896 he was still some six months younger
than the official minimum age.
Walker writes that
Einstein did well in the intermediate diploma examinations; in fact he obtained
the highest overall grade of the six candidates. (Marić came fifth.) It is true
that he fared less well at the final diploma examination in 1900, but during
the previous two years he had become more engrossed with following up his own
interests in physics, and neglected his college studies (hence the reprimand
for poor attendance on one course cited by Walker). He borrowed the meticulous
notes of his friend Marcel Grossman for some subjects to enable him to revise
for the final examination, and achieved a creditable overall grade of 4.91
(grades 1 to 6).
Walker writes that Einstein’s
“questionable 4.91 average” trailed “well behind” the other students who passed
the examination. In fact, in terms of the grading system from 1 to 6,
Einstein’s grade average was approximately equivalent to 78%. This was only
about 5% below the candidate immediately above him (Ehrat, grade average 5.14),
and around 11% below the top candidate (Kollros, 5.45). Compare this with the
fact that Marić’s average grade of 4.00 was about 18% below Einstein’s. Walker also fails to note
that the other students’ grades were not strictly comparable, as they majored
in mathematics. (In the subjects that overlapped, Einstein’s results were on a
par with those of the three other candidates who were awarded a diploma.)[11]
Walker’s efforts to demonstrate that Einstein “barely
satisfied the requirements for the degree” (actually a teaching diploma) can
only be in the interests of indicating that his talents were not exceptional
enough to explain his achievements except by presuming that he had had the
assistance of Marić. (He writes that Einstein’s
work was “no longer filled with daring concepts” after he separated from
Marić in 1914.) This is absurd on two counts. First, though Einstein’s academic record at the Polytechnic (as
against his extra-curricular research) was relatively modest, Marić’s was
consistently worse, and she failed the diploma examination. If the argument is
that Einstein’s record in some way precludes the possibility that he could have
produced the celebrated 1905 papers without assistance, then one would have to
look elsewhere than to Marić for that help. Second, Einstein’s
communications with first-rate physicists in the years following the 1905
publications show unequivocally that he was more than equal to the role of one
of the pre-eminent physicists of his day, and his stature was recognized by
physicists of the calibre of Planck, Lorentz, Nernst, Sommerfeld, Born, Bohr,
and many others.
In relation to the question of
Einstein’s knowledge of the famous Michelson-Morley experiment that was of
relevance to the 1905 special relativity paper, Walker writes:
…a careful reading of those
[Einstein/Marić] letters shows only that Marić and Einstein between them had that knowledge [of the
experiment]. All the references that Stachel quotes to show that
Einstein should have known of the Michelson-Morley experiment and been
familiar with Hendrik Antoon Lorentz’s work are taken from Albert's letters to Marić, and not from
any of the other 99 documents in the first volume of the Collected Papers. The
fact that we now know that Mileva and Albert between them had available the crucial
information about the Michelson‑Morley experiment and information about
Lorentz’s work, while at the same time we know that Einstein later professed
little knowledge of these, suggests that Mileva supplied this information and
she therefore was as capable of discovering the principles of special
relativity as her husband!
Where does one
begin to counter such contorted logic? The letters in question are all written
by Einstein, so it is he who had read
the relevant works. (To what extent Marić also studied them is impossible to judge,
as her surviving letters make no mention of any ideas she has on the
topics in question – or indeed of any
extra-curricular topics in physics.) That Einstein’s much later recollections
about when he learned of the Michelson-Morley experiment were apparently faulty
hardly constitutes evidence that it must have been Marić who supplied this
information. The information, after all, came from articles or books, and it
was Einstein who mentioned these, and
he alone who wrote about matters relating to his own extra-curricular
interests, such as motion relative to the ether, in their correspondence. Walker’s arguing that, on
the unjustified assumption that it was she who was first aware of the
Michelson-Morley experiment, Marić was just as capable of discovering the
principles of special relativity is more than a little absurd. How could knowledge of this one experimental
result indicate the capability of
arriving at the principles of special relativity? Many physicists and some
University students would have read of the experiment, but that didn’t mean
they were capable of arriving at the ideas incorporated in Einstein’s special
relativity paper that he produced in 1905. And in any case, the experiment was
but one strand in his thinking that led to the development of the special
theory or relativity.[12] Furthermore, Walker evades not
only that there is not a single known document of Marić’s in which she
provides original ideas of her own, but also that she failed her diploma exam (with especially poor results in the
mathematics component, with less than half the grade of the other five
candidates). Moreover, a letter from close friend Helene Kaufler to her mother
written before Marić received
the diploma exam results in 1900 indicates that she had even by that stage
given up any ambition of following a career involving research in physics.
Kaufler reports that Marić was offered a (provisional) assistantship at
the Polytechnic; however she “did not wish to accept it; she would rather apply
for an open position as librarian at the Polytechnic”.[13]
Incidentally, Walker’s reference to “the other 99 documents
in the first volume of the Collected Papers” is a red herring. Many of these
other documents were not written by Einstein, and scarcely any of them are of a
nature that they might have contained information about the Michelson-Morley
experiment.
On the basis of his dubious
arguments Walker
concludes that “Mileva Marić deserved to be a co-author” of the relativity
paper. Indeed, he writes, her name did
appear on the original manuscript of the paper! As evidence for this he
provides a quotation from a biography
of Mileva Marić by Desanka Trbuhović-Gjurić in which the author claims
that the Soviet physicist Abraham Joffe “called attention to the fact that
Einstein’s three epoch-making articles of 1905 were marked in the original
‘Einstein-Marić’. According to Trbuhović, “Joffe as an assistant to Roentgen, who belonged to the
board of trustees of the Annalen der
Physik, had seen the originals that the editor had forwarded for review. To
this work Roentgen pulled in his summa
cum laude student Joffe, who had the opportunity to see the manuscripts
that are no longer available today.”
These claims have been refuted by Alberto Martínez and, in
meticulous detail, by John Stachel.[14]
In the obituary in question Joffe writes of the 1905 papers that they were
written by “a bureaucrat at the Patent Office in Bern, Einstein-Marity (Marity –
the last name of his wife, which by Swiss custom is added to the last name of
the husband)” – in other words, Albert Einstein. There is no suggestion that
the articles were co-authored. The statement made by Trbuhović concerning Roentgen is nothing but surmise on her part,
based on the erroneous misconception (or rather, misreading) that Joffe had
claimed to have seen the original manuscripts. In any case, as Stachel points
out, “Roentgen was an experimentalist, and there is no reason why a purely
theoretical paper should have been submitted to him for review when two members
of the Curatorium [of Annalen der Physik],
Paul Drude (the editor) and Max Planck, were both outstanding theorists quite
capable of evaluating the paper.”[15]
Walker acknowledges that Joffe’s reference to the 1905 papers
cited a single author, but finds a way of maintaining nevertheless that the
papers must have been co-authored. He writes that “Joffe’s use of
‘Einstein-Mariti’ [in Cyrillic script] agrees with Mileva’s adoption of the
Hungarianized spelling of her Serbian name Marić, a fact that Joffe would
only have known had he seen the original signed by her, since this usage of
“Mariti” apparently is not found in any of the Einstein biographies.” I’ll
leave to Martínez the refutation of
this claim, along with the others:
As for the article ‘In remembrance of Albert
Einstein’, published in 1955, it was an obituary for Einstein. Literally
translated, it reads:
In the year 1905,
in Annals of Physics , there appeared three articles, thereupon beginning three
most important, relevant directions in the physics of the 20th century. Those
were: the theory of Brownian motion, the photon theory of light and the theory
of relativity. Their author – unknown until that time, a bureaucrat at the
Patent Office in Bern, Einstein-Marity (Marity – the last name of his wife,
which by Swiss custom is added to the last name of the husband). (Joffe, 1955: 187, trans. A. M.)
This passage shows that, for example, Walker’s ‘translation’ is a gross
misrepresentation: ‘Their author was “Einstein-Mariti”.’ Likewise, a few other writers have
distorted Joffe’s words to make it seem as though he made a controversial
claim. It is unusual that Joffe this one time happened to refer to Einstein by
the name ‘Einstein-Marity’. But that simple peculiarity does not entail that he
ascribed any authorship to Einstein’s wife. It is clear that Joffe meant that
the author was one person, a male employee at the patent office, namely Albert
Einstein.
Still, proponents of Marić have tried to make
something out of the fact that Joffe happened to write ‘Marity’ instead of
‘Marić’. For example, Walker
claimed that Joffe just had to have seen an original paper, with the name
Marity on it, because otherwise he would not have known the alternative
spelling of Marić, since it ‘apparently is not found in any of the
Einstein biographies’ (Walker, 1991: 123). Again, Walker was wrong. The name ‘Marity’ appears,
for example, in Carl Seelig’s well-known biography of Einstein published in
1954 (p. 29). Moreover, when Joffe first sought to meet Einstein in Switzerland, he
happened to meet Marić (Joffe, 1967: 889). At the time, she used the name
Einstein-Marity.
The key point remains the same. Joffe did not claim
that Marić co-authored or collaborated in any of Einstein’s papers. And he
did not claim that her name was on the original manuscripts or that he ever saw
any such manuscripts. In multiple places throughout his career, like anyone
else, Joffe acknowledged Einstein for having authored the famous works of 1905.[16]
This demonstrates that, as with his other claims to
have provided evidence that Marić should be regarded as co-author of
Einstein’s celebrated 1905 papers, in his February 1991 letter to Physics Today Walker is engaging in a combination of
clutching at straws and wishful thinking.
Addendum
Up to at least November 2005 Walker had a personal website which included
a webpage with the title “Evan Harris Walker looks at Albert Einstein &
Mileva Maric”: http://users.rcn.com/wcri/wcri/Einstein.htm
The
webpage has not been available since early in 2006, and now access by means of
the Archive retrieval Wayback Machine
website “has been blocked by the site owner”.* However, it is of interest to
examine some of the claims made there by Walker.
1.
“Abraham Joffe tells us that he saw the original relativity manuscript ‘and the
name on this paper was Einstein-Marity’.”
This is
false. Joffe did not state that he had seen the original manuscript. (See
above.)
2.
“The Special Theory of Relativity began as a thesis Mileva wrote and submitted
to Professor Weber, her major professor at the ETH [Zurich Institute of
Technology] in Switzerland.
Weber rejected the paper.”
This
statement so inhabits the realms of fantasy that it is difficult to disentangle
it in such a way as to make any sense of it.
Marić had to write a
dissertation for her 1900 diploma examination at Zurich Polytechnic, and, as
she told her friend Helene Kaufler, she hoped to write a Ph.D. thesis on the
same topic (Popović, 2003, p. 56). The topic in question involved
experimental studies of heat conduction (Stachel, 2002, p. 45; Renn &
Schulmann, 1992, pp. 30, 32, 88, n.5 [Letter 20]). Marić gave up hopes of
working for a Ph.D. after she failed the diploma exam for the second time
(Popović, 2003, p. 78), so there was no thesis that Marić submitted
to Weber which he rejected. In any case the topics of her diploma dissertations
were completely unrelated to relativity theory (which subject is never
mentioned in any existing documents written by her).
So what is Walker
writing about? There is a clue in his letter published in Physics Today in February 1989, where he writes that “Mileva never
completed a thesis – at least not one that carried her name.” Now he cannot be
alluding to her diploma dissertations, which she completed for both the 1900
and 1901 Zurich Polytechnic diploma exams. The implication of his writing “at
least not one that carried her name” can only be that she was wholly or largely
the author of a thesis of Einstein’s. Einstein started to work on a thesis
under the supervision of Weber in late 1900 (CP Vol. 1, [Eng. trans.],
1987, p. 154), but this came to nothing, presumably because of his falling out
with Weber in the Spring of 1901 (Renn & Schulmann, 1992, p. 39). The topic
of the proposed thesis was evidently related to thermoelectricity (Renn &
Schulmann, 1992, p. 30). In 1901 he worked with Prof Alfred Kleiner of Zurich University
as his supervisor on a thesis on the kinetic theory of gases (CP Vol.
1, [Eng. trans.], 1987, p. 188) which he submitted in November 1901 (CP Vol. 1, p. 190). Of the thesis
Marić wrote to Helene Kaufler in December 1901: “Albert has written a
magnificent study, which he has submitted as his dissertation…” (Popović,
2003, pp. 79-80). However Kleiner was evidently dissatisfied with the thesis,
and Einstein formally withdrew it early in 1901 (CP Vol. 1, p. 190). (He eventually submitted a thesis on an
entirely different topic to Kleiner in 1905, and obtained his Ph.D. in January
1906.)
It is evident that Walker’s claim that the Special Theory or
Relativity originated in a thesis written by Marić and submitted to Weber
at Zurich Polytechnic has no basis in fact.
3. “The Photoelectric Effect paper began with Mileva
Maric when she was a student of Professor Lenard at Heidleberg. In 1905
Professor Lenard received the Nobel Prize in physics for his experimental work
on the photoelectric effect, the same year the theory of the photoelectric
effect appeared under the name Einstein. In 1922, Albert Einstein received the
Nobel Prize in physics for the theory of the photoelectric effect and in
accordance with the terms of their divorce decree, he turned over every krona,
every pfennig of the Nobel Prize money to Mileva Maric.”
Walker’s claim that
Einstein’s 1905 paper on the photoelectric effect owes its origins to Marić’s attending Lenard’s classes at Heidelberg University (in 1897) is again in the
realms of fantasy. The four-hour lecture course was on theory of heat and
electrodynamics (Collected Papers Vol. 1,
ed. J. Stachel, 1987, p. 59, n.7). We know precisely when Einstein first came
upon Lenard’s first experimental results on the photoelectric effect, reported
in a letter to Marić in May 1901 (Renn & Schulmann, 1992, p. 54). The
experimental results that Einstein explained in terms of quanta in his
celebrated 1905 paper were published by Lenard in 1902. Any connection between
Marić’s attending Lenard’s course in Heidelberg
in 1897-1898 and the 1905 paper exists entirely in Walker’s imagination.
Walker insinuates that the terms of the divorce agreement
relating to the Nobel Prize money were directly connected to the authorship of the
1905 paper on the photoelectric effect. In fact in a letter dated 31 January
1918 Einstein proposed to Marić that (among other financial incentives)
the capital for any future Nobel Prize be deposited in Switzerland and kept in
safe-keeping for their children, while Marić had disposal of the interest,
in order to overcome her reluctance to agree to a divorce (Collected Papers Vol. 8, [Eng. trans.], p. 456). This was
effectively the terms of the divorce agreement later that year – Einstein
retained final authority over the capital, with Marić having full rights
of disposal of the interest (Collected
Papers Vol. 8, [Eng. trans.], p. 584).
4. “The Brownian Motion work came out of the mind of
Albert and from his consuming interest in thermodynamics. Mileva contributed to
the mathematics describing molecular random walk. This mathematics was critical
to the experimental work of the French scientist Jean-Baptiste Perrin
confirming the kinetic theory and showing the existence of atoms.”
Nowhere has Walker ever provided a
scrap of evidence that Marić
contributed to the mathematics used by Einstein in his 1905 paper on Brownian
Motion. Einstein was highly proficient at mathematics, and would not have
needed any assistance on the mathematics required for that paper. (See **
below) On the other hand, in the mathematics component of the 1900 diploma exam
at Zurich Polytechnic Marić achieved only grade 5 on a scale 1 to 12.
(Einstein obtained grade 11.) (Collected
Papers, ed. J. Stachel, 1987, p. 247)
Conclusion
Walker’s assertions quoted above serve to confirm Stachel’s remark to the
effect that on the issue of Marić’s alleged contributions to Einstein’s
work Walker “is
a fantasist, who judges reality on the basis of his own desires” (Stachel,
2002, p. 26).
* Evan Harris Walker died on 17 August 2006.
** In the “Expert Opinion” on Einstein’s Ph.D.
dissertation submitted to Zurich
University in 1905, the
physicist Prof Alfred Kleiner wrote: “The arguments and calculations to be
carried out are among the most difficult ones in hydrodynamics, and only a
person possessing perspicacity and training in the handling of mathematical and
physical problems could dare to tackle them.” The mathematician Prof Heinrich
Burkhardt, who was requested by Kleiner to give his expert opinion, wrote that
“the manner and treatment demonstrates a thorough
command of the mathematical methods involved”. (Collected Papers Vol. 1 [Eng. trans.], 1987, pp. 22-23)
June 2006
Allen Esterson’s
homepage: http://www.esterson.org/
References
Collected
Papers of Albert Einstein, Vol. 1
(1987) (ed. J. Stachel et al), Princeton University Press.
Collected
Papers of Albert Einstein, Vol. 1 (1987). (English trans. by A. Beck.) Princeton University Press.
Esterson, A. (2006). Mileva Maric: Einstein’s Wife.
Martínez, A. A. (2005). Handling
Evidence in History: The Case of Einstein’s Wife. School Science Review, March 2005, 86 (316).
Popović, M. (2003). In Albert's Shadow The Life and Letters of
Mileva Marić, Einstein’s First Wife. Johns Hopkins
University Press.
Renn, J. and Schulmann, R. (eds.)
(1992). Albert Einstein and Mileva Maric:
The Love Letters. Trans. by S. Smith. Princeton University
Press.
Stachel, J. (1989). Letter,
Physics Today, February 1989, pp.
11-13.
Stachel, J. (2002). Einstein from ‘B’ to ‘Z’.
Boston/Basel/Berlin: Birkhäuser.
Stachel, J. (ed.)
(2005). Einstein’s Miraculous Year: Five
Papers That Changed the Face of Physics. Princeton University
Press.
Trbuhović-Gjurić, D.
(1983). Im Schatten Albert Einsteins: Das
tragische Leben der Mileva Einstein-Marić. Bern: Paul Haupt. French translation (1991): Mileva Einstein: Une Vie. Paris: Antoinette Fouque.
Walker, E. H. Letter,
Physics Today, February 1989, pp. 9-11.
Walker, E. H. Letter,
Physics Today, February 1991, pp.
122-123.
NOTES