Bounds of characteristic polynomials of regular matroids

A regular chain group $N$ is the set of integral vectors orthogonal to rows of a matrix representing a regular matroid, i.e., a totally unimodular matrix. Introducing canonical forms of an equivalence relation generated by $N$ and a special basis of $N$, we improve several results about polynomials counting elements of $N$ and find new bounds and formulas for these polynomials