Math Forum http://mathforum.org/kb List of forum topics en Commutative Diagrams http://mathforum.org/kb/thread.jspa?messageID=8171938&tstart=0#8171938 it is usually stated (see e.g. the introduction of Lang's
algebra) that a diagram commutes if every triangle or
square of which it is]]> Jan 27, 2013 7:52:26 AM Jan 27, 2013 10:29:56 AM Maury 0