# When is a triangular matrix totally unimodular?

I have an {0,1}, invertible, triangular matrix, that I would like to show to be totally unimodular. Are there any known results on the total unimodularity of classes of triangular matrices?

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There is a sufficient condition on the "unimodular" wikipedia page, but I don't know anything beyond that. –  S. Carnahan Jun 14 '10 at 16:14