Updates of two old papers

Updates of two old papers

[Charles Wells]

a) I have uploaded to

http://www.cwru.edu/artsci/math/wells/pub/pdf/sketch.pdf

a version of my 1993 sketches paper with an addendum listing a few
relevant papers not included in the original work.   I have not kept
up with the field well enough to contemplate a complete revision of
the 1993 paper.

b) There has recently been an uptick in citations to my paper [1].
Several works over the years ([2], [3], [4]) have given proofs of my
theorem that are easier to understand and more informative, so I have
posted a package here

http://www.cwru.edu/artsci/math/wells/pub/pdf/AGEPackage.pdf

that contains the original paper, a correction I published later, and
the references below.  Malfait's article in particular embeds my exact
sequence into a remarkable cube of exact sequences.

[1] Charles Wells, Automorphisms of group extensions, Trans. Amer.
Math. Soc, 155 (1970), 189-194.

[2] Kung Wei Yang, Isomorphisms of group extensions.  Pacific J. Math.
Volume 50, Number 1 (1974), 299-304.

[3] D.J.S. Robinson, Applications of cohomology to the theory of
groups, Groups – St. Andrews 1981, LondonMath. Soc. Lecture Notes vol.
71 (1982), pp. 46–80.

[4] Wim Malfait, The (outer) automorphism group of a group extension.
 Bull. Belg. Math Soc. 9 (2002), 361-372.

c) I recommend that more people update their papers in the manner I
have updated these two.  I did it by making a new PDF file with the
added references and then using Acrobat to combine it with the old
paper into one file.  That way I didn’t have to re-TeX the old paper
(in the case of the sketches paper), which is a good thing, since I
don’t know where some of the .sty files are.

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