Affiliation: | (1) Department of Computer Science, University of Toronto, 10 King's College Road, Toronto, Ontario, Canada M5S 3G4 (e-mail: sacook@cs.toronto.edu), CA;(2) The Fields Institute for Research in Mathematical Sciences, 222 College Street, Toronto, Ontario, Canada M5T 3J1 (e-mail: pachl@acm.org), CA;(3) School of Mathematics and Statistics, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario, Canada K1S 5B6 (e-mail: ipress@math.carleton.ca), CA |