Similarity of graphs and enumeration of dissimilar nth order symmetric sign patterns

Introduces the concepts of similarity of n^th order symmetric sign patterns and similarity of n-vertex labelled directed graphs. Two sign patterns are similar if and only if their corresponding directed graphs are similar. A formula to count the maximum number of mutually dissimilar directed graphs and two algorithms are presented. One algorithm generates a set of mutually dissimilar directed graphs and the other tests similarity of two directed graphs.