I have discovered that a blank line in version 3 of the diagram documentation that I sent out the other day has caused errors. Here is the correct paragraph: In homological algebra one often has a $3\times3$ diagram, with or without 0's on the margins. There is a macro to do that: \begin{verbatim} $$\bfig \iiixiii(0,0)|aammbblmrlmr|/>`>`>`>`>`>`>`>`>`>`>`>/<500,500>% {'5436}<400,400>[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w'] \efig$$ \end{verbatim} that gives $$\bfig \iiixiii(0,0)|aammbblmrlmr|/>`>`>`>`>`>`>`>`>`>`>`>/<500,500>% {'5436}<400,400>[A'`B'`C'`A`B`C`A''`B''`C'';f'`g'`f`g`f''`g''`u`v`w`u'`v'`w'] \efig$$ Sorry about that.