On digraphs and forbidden configurations of strong sign nonsingular matrices (Q1809099)

A square real matrix \(A\) is called a strong sign nonsingular matrix (or \(\text{S}^2\text{NS}\) matrix) if all matrices with the same sign pattern as \(A\) are nonsingular and the inverses of these matrices all have the same sign pattern. The digraph associated to an \(\text{S}^2\text{NS}\) matrix is called an \(\text{S}^2\text{NS}\) digraph. The author constructs infinitely many minimal forbidden digraphs (MFD) for \(\text{S}^2\text{NS}\) digraphs which cannot be obtained by vertex- or arc-splittings from other MFDs.