论文部分内容阅读
Let A be a real matrix or a sign pattern of order n. N-(A) denotes the number of negative entries in A. In 1972 R DeMarr and A Steger conjectured: If A is a real matrix of order n such that A2≤0, then N_(A2)≤(n-1)2+1. Now the conjecture is proved to be tr