Simplification of a recent result on robust schur stability of a complex-coefficient polynomials set with coefficients in a diamond

In a previous paper (Yen and Zhou, J. Franklin Inst. 1996), Schur stability of a family of polynomials with transformed coefficients varying in a diamond was studied. A necessary ad sufficient condition was given for the stability of the entire family if a selected set of 16 (for even n) or 32 (for odd n) edge polynomials is stable. In this note we show that the number of edge polynomials to be checked for odd n can be reduced to 16.