摘要
The index of convergence k（A）of a square Boolean matrix A is defined to be the least nonnegative integer k such that A<sup>k</sup>= Ak<sup>1</sup> for some k<sub>1</sub>】k; and the index of convergence k（D） of a digraph D is just the index of convergence of the adjacent matrix of D. Schwarz, Heap,
