Affiliation: | aDepartment of Mathematics, Ben Gurion University of the Negev, PO Box 653, Be'er Sheva, Israel;bLIX, INRIA Futurs, Ecole Polytechnique, 91128 Palaiseau Cedex, France;cDepartment of Computer Science, Ben Gurion University of the Negev, PO Box 653, Be'er Sheva, Israel;dVakgroep Zuivere Wiskunde en Computeralgebra, Ghent University, Krijgslaan 281, Gebouw S22 B9000, Gent, Belgium |