1. Computational and Applied Mathematics, Rice University, 6100 Main Street, MS 134, Houston, Texas 77005-1892. E-mail: borcea@caam.rice.edu.
2. Stanford University, Department of Mathematics, Stanford, California 94305. E-mail: papanico@math.stanford.edu.
3. University of Chicago, Department of Mathematics, Chicago, Illinois 60637. E-mail: tsogka@math.uchicago.edu.