The message of Robert McGrail on 2002-08-23 raises a question: How did the second (1994) printing of Mac Lane and Moerdijk's "Sheaves in Geometry and Logic" (SGL) differ from the first (1992)? The difference was evidently nontrivial, as its review (96c:03119) in MR is specifically of the "Corrected reprint of the 1992 edition.", and the review was evidently delayed until such a corrected reprint could appear. I believe the question is worth asking, as many individuals and libraries have the first printing, and may not have the financial wherewithal to purchase another copy unless it is really vital. (My efforts to locate an errata on the web at all the likely (to me) places have been unavailing.) A (less significant) follow-up question: Did the recently announced third printing contain any further changes? In case it matters, here is the relevant part from the cited email:

You will find this in MacLane and Moerdijk, Sheaves in Geometry and Logic. Check the index for "heyting algebras: of subobjects". I have the first printing of the first edition in which this result is Proposition 1 of the 8th section of chapter III.

Best wishes, Keith Harbaugh _________________________________________________________________ Join the world=92s largest e-mail service with MSN Hotmail. http://www.hotmail.com