Between d-stability and sign-stability: the 3 × 3 case

2] introduced a decreasing sequence of sets of real n × n matrices, which begins with the D-stable matrices and stops at the sign-stable matrices. It is not clear how many of the n sets in the sequence are distinct. This article documents the disappointment that in the first case where the sequence could contain a set which is neither the D-stable matrices nor the sign-stable matrices(viz., the case n = 3) it doesn't.