Affiliation: | Department of Mathematics, University of Illinois at Urbana-Champaign, 1409 West Green Street, Urbana, Illinois 61801 ; Department of Mathematics and Computer Science, Eastern Connecticut State University, Willimantic, Connecticut 06226 ; Department of Computing, Macquarie University, Sydney, NSW 2109, Australia ; Department of Mathematics and Computer Science, Eastern Connecticut State University, Willimantic, Connecticut 06226 |