Updates to Chapter 17, "Farewell, My Lindgren",
in Dissections: Plane & Fancy, by Greg N. Frederickson:

Citing Lindgren's work correctly

The citation for Harry Lindgren's 13-piece dissection of three hexagrams to one should be (1964b). The citation for his 12-piece dissection should be (1964a), which incidentally should be entitled "Dissections for Schools". The figures for that article do not appear on pages 52-54, but rather in the Supplement.
(This is corrected in the paperback edition.)
Also, the citation for Lindgren's 18-piece dissection of three enneagons to one should be (1964a).

Another dissection found by Ernest Freese

In Ernest Freese's manuscript, Geometric Transformations (completed before his death in 1957), which I got access to in February 2003, there is a diagram (on Plate 86) of the same 12-piece dissection of three hexagrams to one that Harry Lindgren published in 1964.

Abu'l-Wafa produces the square root of 3

In Figure 17.15, I used a certain trick to produce the side of the large octagon. You will see six identical pieces in my dissection, and construction of these pieces relies on the trick. This trick was described much earlier in Abu'l-Wafa's manuscript "On the Geometric Constructions Necessary for the Artisan". The trick, along with an accompanying figure, is discussed in the article "Mathematics and Arts: Connections between Theory and Practice in the Medieval Islamic World", by Alpay Özdural, Historia Mathematica, vol. 27 (2000), pp. 171-201.

C. Dudley Langford was a chemist

I made a mistake in the biography of C. Dudley Langford, claiming that his Ph.D. was in mathematics. Actually, all of his degrees were in chemistry, as he states in a letter to Harry Lindgren dated August 11, 1962.

Robert Reid passed away

I am sorry to report that on April 26, 2016 Robert Reid passed away in London, England. He was an amazing man and will be missed by many.
Martin Watson has written a wonderful summary of Robert's life. It includes photographs from Robert's boyhood, his young adulthood, and his last two decades back in London. Martin also found and included two remarkarble videos, one in which Robert appears in a Chiclets commercial produced in Peru, and another in which Robert Robert appeared in a Spanish-language Peruvian-Argentinian production, `El Inqusidor' (The Inquisitor'). Martin also included photos of some of Robert's non-dissection mathematics work.

A clue!

Our favorite private mathdick has uncovered a valuable clue that may lead to important discoveries: The official name of an {11} is a "hendecagon", according to John Conway, at Princeton. Now don't go out and get yourself busted.

Copyright 1997-2017, Greg N. Frederickson.
Permission is granted to any purchaser of Dissections: Plane & Fancy to print a copy of this page for his or her own personal use.

Last updated July 28, 2017.