<Verb>HomotopyGraph(Y):: RegCWComplex --> Graph</Verb><P/>

<P/> Inputs a regular CW-complex  <M>Y</M> and returns a subgraph
<M>M \subset Y^1</M> of the <M>1</M>-skeleton
for which the induced homology homomorphisms
<M>H_1(M,\mathbb Z) \rightarrow H_1(Y,\mathbb Z)</M> 
and <M>H_1(Y^1,\mathbb Z) \rightarrow H_1(Y,\mathbb Z)</M> have identical 
images. The construction tries to include as few edges in  <M>M</M> as possible, though a minimum is not guaranteed.


