The algorithm constructed here is based on a new way to compute powers
of matrices, which we will call the Hedetniemi matrix sum. This sum was
suggested to Nystuen at the University of Michigan by S. Hedetniemi, who was
then a graduate student in mathematics. Hedetniemi later completed his doc-
Chapter 18 Shortest Path Problems 325
torate under Frank Harary; and Nystuen, a professor of geography at Michigan
remembered the method for later application.