This is a package of commutative diagram macros built on top of Xy-pic by
Michael Barr (email: barr@barrs.org). Its use is unrestricted. It may be freely
distributed, unchanged, for non-commercial or commercial use. If changed, it
must be renamed. Inclusion in a commercial software package is also permitted,
but I would appreciate receiving a free copy for my personal examination and
use. There are no guarantees that this package is good for anything. I have
tested it with LaTeX 2e, LaTeX 2.09 and Plain TeX. Although I know of no reason
it will not work with AMSTeX, I have not tested it.