# How to prove in a graph $G$, its incidence matrix $A$ is totally unimodular if and only if $G$ is a bipartite graph?

I'm learning network and transportation model. The question is not from my homework. I'm just curious about:

In a graph $G$, its incidence matrix $A$ is totally unimodular if and only if $G$ is a bipartite graph.

Could anyone good at proving give a simple provement?

OR

Could anyone provide some related materials?

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Most books with "integer programming" in their title will have a proof of this. –  Chris Godsil Nov 13 '12 at 23:49