Errata for "The William Lowell Putnam Competition 1985--2000: Problems,
Solutions, and Commentary" by Kedlaya, Poonen, Vakil

[From Richard Stanley, received 5 Nov 03]
page 68: the "related question" is incorrect: consider the matrix
     1 1
     0 0
More precisely, the condition that each traversal sums to m should be 
that each row and each column sums to m. Then this statement indeed becomes
the discrete version of Birkhoff-von Neumann.

[From Frederic Latour, received 9 Jan 04]
page 91: in Figure 8, the fraction 3/2 at far right should be 2/3.

[KSK, posted 28 Jun 04]
page 279: The second "related question", asking whether the set
   S = {a^2 + b^2: a, b in Z}
contains an arithmetic progression of length k for any integer k >= 1,
appears to have been resolved. Ben Green and Terry Tao have recently announced
(see their paper arXiv: math.NT/0404188) a proof that any subset of the prime 
numbers of positive relative upper density contains arithmetic progressions of
arbitrary (finite) length. Since the set of prime numbers congruent to 1 mod 4
has relative density 1/2 within the prime numbers, and any such prime can be
written as a^2 + b^2 for some a and b, this implies that indeed S contains
an arithmetic progression of any finite length.

[KSK, posted 30 Jun 04]
page 126: the last two lines of the statement of B4 should be in boldface.

[BP (from his mother), posted 8 Nov 04]
page 281: the label P_8 is missing from Figure 42.

[from Joe Keller (via RV), posted 21 Nov 04]
page 285: the "stationary phase approximation" is due to Kelvin.