We denote by Q(A) the set of all matrices with the same sign pattern as A. A matrix A has signed null-space provided there exists a set S of sign patterns such that the set of sign patterns of vectors in the null-space of (A) over tilde is S for each (A) over tilde is an element of Q (A). Some properties of matrices with signed null-spaces are investigated.
SIAM Journal on Matrix Analysis and Applications
Kim, S. J.; Shader, Bryan L.; and Hwang, S. G. (2002). "On Matrices with Signed Null Spaces." SIAM Journal on Matrix Analysis and Applications 24.2, 570-580.