Thanks Taco.  I'm sure I'll get the hang of the new tabular commands eventually - though reproducing the example on pp. 274-5 of the Not so Short Introduction doesn't quite work (the second column is shifted a line down from the first column - but I guess there's something I should have set up initially to get it to work).

It's not the definition of \yogh that would cause me any difficulty, but the fact that I can't say:

\defʒ