\Chapter{Authors' Addresses}

Bettina Eick

Fachbereich f\"ur Mathematik und Informatik, Universit\"at Kassel, 34109 Kassel, Germany

www.mathematik.uni-kassel.de/$\sim$eick

eick@mathematik.uni-kassel.de

\bigskip

Charles R.B. Wright

Department of Mathematics, University of Oregon, Eugene, Oregon 97403, U.S.A.

www.uoregon.edu/$\sim$wright

wright@math.uoregon.edu