Petr Zimaserves on the faculties of three Canadian institutions�and is the coauthor of several works in financial mathematics and operations research.Robert L. Brown, F.S.A., F.C.I.A., A.C.A.S. (Waterloo, Ontario, Canada), is a professor in the Department of Statistics and Actuarial Science at the University of Waterloo, Waterloo, Canada. He is author of three books and coauthor of a recent textbook in the mathematics of finance.