1. Méthodes et Algorithmes pour la Bioinformatique, LIRMM, CNRS, Université de Montpellier, 34392 Montpellier Cedex 5, France
2. Department of Statistics, University of Auckland, Auckland 1142, New Zealand
3. Institute of Computational Science, ETH, CH-8092 Zurich, Switzerland
4. Swiss Institute of Bioinformatics, CH-1015 Lausanne, Switzerland
5. Department of Statistics, University of Oxford, OX1 3TG Oxford, UK