(Don’t
be alarmed by discrepancies between what is written below and what is written
in some of the MGP entries. The latter are being revised and so the problem is
only a temporary one. Some links are to draft entries.)
The UK has an unbroken tradition of 800
years of university mathematics but
for nearly all of that time the creation of doctors played no part in the process of preparing the next generation of
mathematicians. The PhD is new to
the UK, compared to Germany or even to the United States (see NSF US Doctorates). It
appeared at the end of the First World War and it was not until after the
Second that a PhD became part of the usual preparation of a university mathematician.
There may be a chain of teachers back to Bradwardine
(d. 1349), to Newton (d. 1727), to Cayley
(d. 1895) but there is no
chain of doctors.
Today’s entrants into academic
mathematics typically have PhDs and they may have some post-doctoral research
experience as well. See the advertisements for Academic Jobs on the London Mathematical
Society’s website. (The LMS (MacTutor)
is the UK’s
national association for Mathematics.)
The past was very different but,
because people and practices last, not so very remote. CoxeterMGP
was supervising PhDs until the 1980s. His own PhD, awarded in 1931, was
supervised by H.
F. BakerMGP who graduated in 1888!
A first degree was Baker’s qualification for a distinguished career in pure
mathematics. T. M. F. Smith was President of the Royal
Statistical Society in 1991-3. His qualification was also a first degree,
awarded in 1959. In 1888 the first degree was absolutely standard, in 1959 it
was unusual, but not as unusual as Coxeter’s PhD in 1931. The production of
PhDs by means of PhDs is a recent phenomenon.
Do not be surprised to find supervisors (advisors)
with only a first degree.
Do not expect long lines of
descent. The PhDs before 1940 were almost necessarily ‘first
generation’ PhDs but for decades afterwards the system contained many
supervisors without PhDs.
Do not expect uniformity. The
percentage of people entering academic mathematics with PhDs went from 0
in 1920 to nearly 100% today but the movement was not uniform over time,
nor uniform across branches of mathematics. The PhD as entry requirement
came sooner to pure mathematics than to statistics.
The aim of these notes is to save the user of MGP from jumping
to too many wrong conclusions. Wrong
conclusions cannot be entirely avoided for there are wrinkles enough in the
system to confuse anybody. One wrinkle—of historic interest only
now—illustrates how qualifications may not be what they seem.SylvesterMGPcompleted his studies at St. John’sCollege,
Cambridge in
1837. Not being a member of the Church of England (he was a Jew) Sylvester was
disqualified from graduating from Cambridge.
However, his work at St John’s
was recognised by Trinity College Dublin and he was awarded a BA (and an MA)
from that institution in 1841. He never
studied at Trinity. There are equally surreal PhD stories. In 1929 WittgensteinMGP
was awarded a PhD by CambridgeUniversity. He had been a
student of Russell
but left in 1913 without a degree. In 1929 RamseyMGPwas
designated his supervisor and Wittgenstein presented as his thesis a work
written 10 years before, away from Russell, away from Cambridge and while
Ramsey, 14 years his junior, was still at school.
Notes on the
History of the PhD
The image of a PhDsystem has been present since 1850, there
has been a PhD degree since 1920 and a functioning PhD system since around
1950. These notes describe how these changes took place and give some basic
information about British degrees and practices. Today there are more
than 100 universities in the UK;
see here for links to maths departments and here and here for graduate programmes. The universities
frame their own degree regulations and these, beyond a basic similarity, are
quite varied. I have not written a survey of these institutions, nor a key to
how each institution has interpreted the letter D in the course of its
history. Further, the notes treat only the UK,
although, through the British Empire and
Commonwealth, British thought and practice about universities have influenced
developments all over the world.The
historian Hank Nelson discusses the PhD in Australia;
see also Ian D. Rae (2002) False Start for the PhD in Australia, Historical Records of Australian Science, 14(2) 129-141 abstract. In Canada where the influence of the United States
was much stronger the PhD came much earlier: for references see the notes
to M. L. Friedland The University of
Toronto: A History.
General References
The basic
reference for the origins of the PhD is Renate Simpson How the PhD came to Britain. A Century of Struggle
for Postgraduate Education, Society for Research into Higher
Education, 1983.
Renate Simpson has just published The Development of the PhD Degree in Britain,
1917-1959 and Since: An Evolutionary and Statistical History in Higher
Education, Mellen
Press. This treats the first fifty years of the PhD system in Britain.
The mathematicians of the transition period are very
well served by two databases, June Barrow-Green's BritMath and A E L
Davis’s Mathematical
Women in the British Isles, 1878-1940. BritMath provides
detailed information on 750 mathematicians from the period 1860-1940. Mathematical
Women gives the qualifications of all the 2500 women who
graduated in mathematics between 1878 (when women were first admitted) and
1940. Of the BritMath mathematicians about 150 have PhDs.
To illustrate the varieties of personal experience
I have made links to the biographies in John O’Connor & Edmund
Robertson’s MacTutor
History of Mathematics Archive. For additional colour there are links
to the title pages of books where authors can be seen displaying their
qualifications.
800 years of mathematics in Oxford
(the oldest university in the British Isles)
are surveyed in Oxford Figures: 800
Years of the Mathematical Sciences edited by John Fauvel, Raymond
Flood and Robin Wilson, Oxford University Press 1999. (Amazon.)
See also I. W. Busbridge Oxford Mathematics and
Mathematicians.
For the
Scottish university scene see Stuart
Wallace “National Identity and the Idea of
the University in 19th-Century Scotland” Higher
Education Perspectives, 2, 2006.
The
standard reference work on the universities of the Commonwealth is the Commonwealth Universities Yearbook
published by the Association of Commonwealth Universities London.
19th Century
In 1800, as in 1600, there were
two universities in England,
four in Scotland (MacTutor)
and none in Wales or Northern Ireland—Trinity College Dublin was the only
university in Ireland.
The national scientific academy, the Royal
Society of London (MacTutor)
dates from 1662. Election to its fellowship, indicated by the initials FRS, was (and is) a prized distinction.
In 1800 the English universities, Oxford and Cambridge, were nothing
like modern research universities and almost moribund compared to the two main
Scottish universities, Edinburgh
and Glasgow. In
the course of the 19th century the old universities were reformed and new ones
were created. Mathematical Women gives a list
of the universities awarding degrees in mathematics in the early 20th century;
today there are many more. It also gives the numbers of students graduating
(men as well as women) from each institution, which gives some idea of the
scale of university mathematics. Information on the number of academics in each
institution can be found from BritMath.
Reference
The two English universities in 1800, Oxford and Cambridge,
are placed in a European context in L. W. B. Brockliss “The European
University in the Age of Revolution, 1789-1850” ch. 2 of The History of the University of
Oxford, volume VI: Nineteenth-Century Oxford (eds. M. R. Brock & M. C. Curthoys), Clarendon
Press, Oxford 1997. (Amazon.)
First
degrees, BA and MA
In the 19th century and for many
years after the introduction of the PhD in the 20th century the standard
degreequalification of the university mathematician was a BA or MA; see
e.g. this title
page from Todhunter,
this
from HardyMGPor this from
FisherMGP.
For most of the 19th century the only
mathematics degrees were first degrees—in today’s terms.At Oxford and Cambridge the Bachelor of
Arts (BA) was awarded on the basis of the student’s examination performance.
The Master of Arts (MA) involved no further academic work and was essentially a
formal recognition that the person actually was a BA! This is still the case in
Oxbridge; see here
for the current Cambridge
practice. The MA was required for full membership of the university and so
university teachers were invariably MAs. The existence of two degrees, awarded
at different dates for the same course of study, is a source of confusion and
explains some of the discrepancies in the dates given by different authorities.
In Scotland
the first degree was, and is still, called the MA.
The University
of Cambridge was the centre of
mathematical teaching and research in Britain
in the 19th century and the first half of the 20th: “The study of Higher
Mathematics in the British Empire is now practically concentrated at Cambridge” wrote the Times newspaper in 1906. More than
two-thirds of those listed in BritMath were students at Cambridge and Cambridge
figures dominate the MacTutor biographies. The
Cambridge Mathematical Tripos had great prestige and success in it was widely
regarded as the best qualification for an academic career in mathematics.
Indeed until the Second World War graduates from other universities would take
the Cambridge degree (or part of it) as a form of post-graduate study: JeffreysMGP, HodgeMGP and DavenportMGP
are instances. Jeffreys, for example, had two first degrees; the later ‘higher’
degree is the one given on the MGPpage.
The new faculties of the old
universities and the new universities created in the 19th and 20th centuries
used the established terms Bachelor and Master for their degrees, although the
new institutions did not follow the ancient universities’ practice of
conferring an MA upon a BA. Some universities adopted the name Bachelor of
Science (BSc) for their degree in mathematics. The post-graduate Master’s
degree is a fairly recent development. It is rare in pure mathematics but since
the 1960s it has been widely offered in statistics.
Sources
Andrew Warwick Masters
of Theory:Cambridge
and the Rise of Mathematical Physics, ChicagoUniversity
Press, 2003. (Amazon.)
This contains a very thorough study of the mathematics tripos in the 19th century.
(The British mathematical physicists of the 19th century had degrees in
mathematics.) There is a useful review by Grattan-Guinness in the SIAM News.
Doctorates, higher
and honorary
The doctorates existing in 1800
were in Divinity, Law, Medicine and Music. Dr
Wallis, the Savilian
professor of geometry at Oxford 1649-1703, was a doctor of divinity,
DD, because he was a theologian before he was a mathematician. These doctorates
were not like the modern PhD for the award recognised an established reputation
in a field, not the quality of a piece of work done at the beginning of a
career. In the course of the 19th century
doctorates in other subjects were created on the same pattern.
In 1882 Cambridge
introduced the ScD, a doctorate open to Cambridge
graduates who had produced a significant body of scientific work; a LittD for
scholarship in the humanities was also created. Other universities established
similar degrees. The British university is not generous with titles, for only a
minority of academics have the title “professor”, and perhaps the move was a
case of keeping up with titled foreigners. The award of the ScD did not mark
the beginning of a career, it recognised a successful career. Writing in the
20th century, Jeffreys
described the Cambridge ScD as “more or less equivalent to being proposed for
the Royal Society.” Jeffreys himself submitted work for the equivalent degree
at the University
of Durham and was awarded
its DSc. Many distinguished graduates took advantage of this doctoral
possibility, but not all; the title
page of Whitehead
& Russell’s
Principia Mathematica shows one
author with an ScD, one without. Following the creation of the PhD, the term higher
doctorate came to be used for the ScD, or its equivalent elsewhere (most
often denoted by DSc). British universities still award higher research degrees
but today almost all of those receiving them have a PhD already. See here
for what Cambridge
expects of an ScD today and here
for an application form.
Edmond
Halley, Wallis’s successor at Oxford,
was made a Doctor
of Civil Law in 1710. This was not in recognition of any distinction in law
but in recognition of Halley’s scholarship in producing an edition of
Apollonius’s Conics. Samuel Johnson, the poet and dictionary maker, was
a later recipient of an honorary doctorate from Oxford: “they have sent
me a degree of Doctor of Laws, with such praise in the Diploma as perhaps ought
to make me ashamed …” In the 19th century James
Clerk Maxwell (title
page) was an honorary doctor of law from Edinburgh University. Another LLD
was E.
J. Routh; Routh, unlike Maxwell, lived to collect a Cambridge ScD as well (title
page). Honorary doctorates are still conferred by British universities;
which particular title is chosen will vary with the university but the title is
never PhD.
The Jeffreys quote is in
David Howie (2002) Interpreting
Probability: Controversies and Developments in the Early Twentieth Century,
New York,
Cambridge University Press.
The UKCGE
has recently surveyed Higher
Doctorate Awards in the UK.
The story of the
award of Johnson’s honorary doctorate in March 1775 is told in Boswell’s Life of
Johnson.
Early
research degrees, fellowship dissertations, Smith’s Prize essays
In the 19th century British
university reformers looked to Germany
for a model of the modern university and the higher degree was an element in
the German system. Higher degrees to follow on from a bachelor’s degree and
serve as a preparation for an academic career started to appear in the 1860s.
The DSc introduced by LondonUniversity in 1860 was a
higher degree for advanced study
rather than research and was assessed by examination but the Edinburgh DSc had
an element of research. In 1885 the London
regulations were changed and the DSc became a genuine research degree; Charlotte
ScottMath
WomenMGPwas awarded a DSc in
1885, at the end of the examination era. In 1895 all the Scottish universities
adopted a five year research degree open to graduates from other universities.
In Cambridge there was no feeling that a
research degree was necessary for its own graduates but the university created
a Bachelor of Arts by Research for graduates from other universities; this
could be completed in one year. This was not a popular degree and BritMath lists only one person
with it, appropriately the unique Ramanujan.
The BA by Research was a curiosity but there were two other research
developments that had a lasting influence on mathematical life in Cambridge.
Cambridge men had two opportunities to
impress, the tripos examinations and the Smith’s Prize, the latter a
competition open to the best students. Originally the Smith’s Prize was based
on written examinations but from 1885 it was awarded for the best essay. The prize became the focus for
post-graduate research as students might spend a year working on their
entry. In the early days, at least, there was no system of supervision and so
no declaration of ‘parentage.’ Sometimes there was a clear supervisor, e.g. Barnes’s
supervision of LittlewoodMGP entered the lore of
mathematics. Smith’s Prize Winner did
not appear with MA after the person’s name but it was a very significant
qualification and the list of winners given by Barrow-Green is a
who’s who of Cambridge
mathematics. In 1936, when Fred
HoyleMGP
began his research career, his objective was the prize since “gaining either a
Smith’s or a Rayleigh was considered to be almost a guarantee of a post in some
university.” The Rayleigh Prize was
an additional prize first awarded in 1911. As well as the winners, other
creditable performers would be named; in 1935 altogether 9 names appeared.
After the Second World War, as the PhD system became established, submitting an
essay became a stage in the making of a PhD.
The other innovation
was the fellowship dissertation. In 1872 TrinityCollege
introduced the dissertation into its fellowship competition and some other
colleges followed. See, for example, the MacTutor entries for A.
N. WhiteheadMGPand H.
W. RichmondMGP. Fellowship dissertations
continued into the PhD era—see P.
Hall MGP—and
still exist. Both Cambridge
developments are illustrated in the careers of Louis
Mordell MGPfrom the 1910s and Alan
Turing from the 1930s.
Mordell’s essay for the Smith’s Prize was successful but his fellowship
dissertation was not. For Turing one essay was successful both as a Smith’s
Prize entry and as a fellowship dissertation. Subsequently Turing went to Princeton for a PhD MGP.
Like J.
H. C. WhiteheadMGP
, from Oxford, Turing was attracted to Princeton
by the opportunity of working with a particular supervisor, rather than by the
PhD qualification which was not required for a career in Britain.
It was possible to go abroad for
a PhD but there was little incentive to do so. In the nineteenth century it
became a tradition for British chemists to go to Germany to obtain a doctorate but
in other subjects it was unusual to go abroad. BritMath has two instances of
mathematicians with foreign PhDs from the era before the First World War: Grace
Chisholm YoungMath
WomenMGP
with a PhD from Göttingen and Harry
BatemanMGPwith
a PhD from Johns Hopkins. Both were unusual cases. As a woman, Miss Chisholm
had very restricted opportunities in Britain. Bateman already had 60
publications and the most likely explanation for his wanting a PhD is that in America, where
he was working, an academic was expected to have one. At Johns Hopkins, thirty
years before, SylvesterMGPhad
been in at the birth of the US
doctoral system but his career as a PhD supervisor ended when he returned to England.
For Sylvester’s activity in America
see Parshall & Rowe “American Mathematics comes of Age: 1875-1900” in AMS
History of Mathematics, Volume 3.
Sources
For the early research
degrees see Simpson chapters 2 & 3.
The Cambridge
research degree was significant in the history of the Cavendish (physics)
laboratory. See ch. 4 of Dong-Won Kim (2002) Leadership and Creativity: A History of the Cavendish Laboratory,
1871-1919, Kluwer. See Google
Book Search for an extract.
For the Smith’s prize see
June Barrow-Green (1999) “A Corrective to the Spirit of too
Exclusively Pure Mathematics”: Robert Smith (1689-1768) and his Prizes at CambridgeUniversity, Annals of Science, 56,
271-316. Appendix 1 lists the winners from 1885 to 1940 with the ‘grades’
their essays received. There is no information about unsuccessful
entries..
Barrow-Green describes
the fellowship dissertation system but there does not seem to be any list
of who wrote what.
20th Century
In 1917 British universities
resolved to create a PhD degree. However, deciding to create a degree is not
the same as deciding that the degree should matter. There was no
resolution to create a system in which the PhD would be an essential part of
the preparation of the university academic. The system evolved without anybody
planning it.
The PhDdegree
By the beginning of the 20th
century the case for a PhD type degree had been made and won—at least outside Cambridge (and Oxford).In 1917 representatives of the universities
met and agreed that they would establish a PhD degree. The key resolution said
For the better promotion of
research in this country, and for the encouragement of advanced work by
“graduate” students from abroad, a degree or title of Doctor should be
instituted, attainable after a period of not less than two years whole-time
work devoted to advanced study or research …
The universities acted together
under strong political pressure. Imperial considerations were important. There
had long been anxiety that students from the dominions would go to Germany or the United States and be weaned away
from the mother country.
Oxford was the first university to institute
such a degree, although its choice of title, DPhil, was idiosyncratic. The
first Oxford DPhil in mathematics was awarded in 1921. The first Cambridge PhD
in mathematics was awarded in 1924 to an Australian Thomas CherryMGP.
A concept of supervision had to
evolve. C.
R. RaoMGP
described his experience as a student in Cambridge
in the 1940s and later as a supervisor in India
and the US.
“I asked Fisher [Rao’s supervisor] to suggest a research problem for my Ph.D.
thesis. He said the problem must be mine and that he would only advise me if
and when I encountered difficulties. This was good advice. I used to say the
same to my Ph.D. students without success. There were only 2 cases (out of 50),
where the students chose their own problems.”The practice in the UK,
until recently at least, has been for a student to have a single supervisor.
Besides the supervised
dissertation, there is another route to the PhD, the staff PhD. A member of staff at a university may obtain a PhD by
submitting published work. There is usually no
supervisor and the staff PhD is more like a baby ScD than a regular PhD. In
1935 F N
DavidMath
WomenMGPwas appointed as an assistant lecturer at University College London; in
1938 she was awarded a PD. “I took it by sending in 4 papers I had already
published.” This route to a PhD still exists; see here for a
typical set of regulations.
H. E. DanielsRSS president 1974-5 MGPwas
awarded an external PhD from the University of Edinburgh;
an external student does not attend the university. Daniels was ineligible for
a staff PhD because he was not working at a university and he was not old
enough for an ScD. “Aitken was nominally my supervisor but hadn’t the faintest
idea of what I was doing.” Daniels did not really need a supervisor, as he was
already a well-established researcher.
On the general issue of the PhD,
David recalled, “You did not need [a doctorate] in England, or you did not need it at
that time anyway.” She also recalled that Karl
Pearson, for whom she had worked, did not think it “a good thing.”
Looking back, Daniels did not seem to think it a good thing either. “[Research]
is about having ideas. What happens with the run-of-the-mill Ph.D. student is
that you lay a trail of clues for him, which he follows, you hope, and in the
end he produces his thesis. Well, it seems to me that this is self-defeating.”
These reminiscences are from
statisticians but the experiences and attitudes they describe have a wider
relevance.
There has been continuing debate
about the character of the PhD and there has been a movement away from the
traditional pattern which involved only research to one involving advanced
courses as well. The EPSRC (the state science funding body) and its
predecessors have been important voices in these debates. The PhD experience is
much more variable than the undergraduate experience. Supervision has ranged
from “Hello, go away and come back when you are finished!” to very close
supervision on a topic worked out in detail by the supervisor. The EPSRC
(and its predecessors) have tried to codify and regulate the process. See the guidelines
for its current model of how student and supervisor should work together. This
document breathes anxiety that the student will not submit the dissertation on
time and late completion has been an issue for decades.
The ET Interview:
Professor C.R. Rao: Interviewed
by Anil K. Bera, Econometric Theory, 19, (2) (2003),
331-340.
N. M. Laird, A Conversation with F N David, Statistical
Science4, (3) (1989), 235-246. JSTOR. Project
Euclid
P. Whittle,
A Conversation with Henry Daniels, Statistical Science,8, (3), (1993) 342-353.
JSTORProject
Euclid
The PhDsystem
British universities have never
been obliged to recruit only PhDs as
lecturers but increasingly they have come to do so. The state played a role in
this. The Department of Scientific and Industrial Research (DSIR),
the body founded during the First World War to support scientific research,
provided scholarships, though only in very small numbers. The number of
scholarships was increased after the Second World War. The Engineering and
Physical Sciences Research Council (EPSRC), the current version
of the DSIR continues to do so.
Simpson’s Development charts the first four decades of the PhD system. She
finds (p. 321) that 23,505 students were admitted to study for the PhD in all
subjects at UK
universities in the period 1917-59. Of these admissions 1230 were to
mathematics. The top four universities were Cambridge
with 568 (46.3% of the total), ImperialCollege with 195 (15.9%), Oxford with 185 (15.0%) and
University College London with 131 (10.7%). Over the decades the numbers grew
although the Second World War stalled the growth: the admissions figures by
decade for the six largest institutions were 96 (1920s), 207 (1930s), 306 (1940s)
and 611 (1950s). Simpson does not report employment destinations.
There is information on the
growing importance of the PhD as a qualification for an academic job in the
research conducted for the inquiry into higher education in Britain which
resulted in the Robbins report. One of the volumes reported on Teachers in Higher Education.
This found that, in 1961-2, 72%
of university teachers in science (the category covering mathematics) had
a doctorate of some kind, including a higher doctorate. In the humanities
the figure was 29%.
It also found that 45% of those recruited in 1959-61 had a doctorate. The
authors comment, “the proportion of teachers with higher degrees is lower
among those who took their first degree within the last ten years than
among older staff, since many of the more recent recruits are of course
still working for a higher degree.” The comment reflects the practice of
hiring people who had not yet completed their PhD and also the possibility
of hiring on condition that the employee starts a PhD. It also reflects
the absence of higher doctorates amongst the recruits.
In 1989 the Science and
Engineering Research Council (successor to the DSIR
and predecessor of EPSRC) set up a committee to review mathematics
education. By then it had become axiomatic that the university mathematician
has a PhD. The Kingman report concluded that the current supply of mathematics
PhDs is “dangerously inadequate.” The report contains some interesting data. It
gave the number of full time academic staff in university mathematics
departments as 1500 with 20 post-doctoral fellows and 120 research assistants.
It estimated that in 1990 around 115 PhD students completed their degree. It
also estimated that to hold current staff levels constant would require
recruitment at the level of 80 posts per year, 30 each in pure and applied
mathematics and 20 in statistics and operational research. There is more recent
information in the 2004 review of UK research in
mathematics which was undertaken by an international team for the EPSRC.
For almost all of its 800 years
the university system was a virtually closed system in which the academics were
recruited from the ranks of local graduates. De
Moivre, the seventeenth century refugee from Catholic France, had no entry
into the universities, while refugees from Nazi Germany in the 1930s,
especially junior people such as H. O.
HartleyMGP,
Bernhard
NeumannMGPand
Richard
RadoMGPoften
entered the system by taking a second PhD. Recently, however, to meet
the shortfall in locally produced PhDs universities have increasingly recruited
foreign mathematicians and university mathematics, like the entire university
system, has become very open.
References and further
reading
Renate Simpson The Development of the PhD Degree in Britain, 1917-1959
and Since: An Evolutionary and Statistical History in Higher Education,
Mellen
Press 2009.
Higher Education: Report of the Committee appointed by
the Prime Minister under the chairmanship of Lord Robbins, 1961-63
Committee on Higher Education: Appendix 3, Teachers in Higher Education.
Cmnd. 2154. London,
Her Majesty’s Stationery Office.
Mathematics: Strategy for the
Future, Report of the
Mathematics Strategy Review Panel chaired by John Kingman, Science and Engineering Research Council.1991.
Some
of the analysis in A. Oswald & S. Machin “UK Economics and the
Future Supply of Academic Economists” Economic Journal, 110, (2000), 334-349 longer
version applies to mathematics.
The PhD is itself the
subject of research: see e.g., this (Australian) paper
‘It’s a PhD not a Nobel Prize’ by Mullins and Kiley on the examining of
PhD theses and the University of Exeter bibliography
for doctoral supervisors.
For a survey of current thinking on the PhD in Britain see C. Park “New Variant PhD: The
Changing Nature of the Doctorate in the UK,” Journal of Higher Education Policy and Management, 27, (2005), 189-207. online
John Aldrich, University of Southampton,
Southampton, UK. (home)February 2006. Latest
changesDecember 2009
I am grateful to June Barrow-Green,
A E L Davis, Anthony Edwards, Karen Parshall, Renate Simpson, Fred Smith and
Brian Stewart for information, corrections and suggestions.