  We consider a family of pairs of m-by-p and m-by-q matrices, in which some
entries are required to be zero and the others are arbitrary, with respect to
transformations (A,B)--> (SAR,SBL) with nonsingular S, R, L. We prove that
almost all of these pairs reduce to the same pair (C, D) from this family,
except for pairs whose arbitrary entries are zeros of a certain polynomial. The
polynomial and the pair (C D) are constructed by a combinatorial method based
on properties of a certain graph.
