European Journal of Combinatorics

Editors-in-Chief Patrice Ossona de Mendez Centre d'Analyse et de Mathématique Sociales (CAMS), Centre National de la Recherche Scientifique (CNRS), 190 avenue de France, 75244 Paris cedex 13, France, Pierre Rosenstiehl Centre d'Analyse et de Mathématique Sociales (CAMS), Centre National de la Recherche Scientifique (CNRS), 190 avenue de France, 75244 Paris cedex 13, France, Founding Editors Michel Deza , Michel Las Vergnas , Pierre Rosenstiehl , Managing Editor Éric Colin de Verdière Département d'Informatique, Ecole Normale Supérieure de Paris, 45, rue d'Ulm, 75005 Paris, France, Editorial Board A. Björner KTH Royal Institute of Technology, Stockholm, Sweden, B. Bollobás University of Memphis, Memphis TN, USA, F. Brenti Università di Roma "Tor Vergata", Roma, Italy, A.E. Brouwer Technische Universiteit Eindhoven, Eindhoven, Netherlands, P.J. Cameron Queen Mary, University of London (QMUL), London, UK, R. Cordovil Universidade Técnica de Lisboa, São João De Deus, Lisboa, Portugal, D. Foata Université Louis Pasteur (Strasbourg I), Strasbourg, France, P. Frankl Peter Frankl Office Ltd., Shibuya-Ku, Japan, K. Fukuda Eidgenössische Technische Hochschule (ETH) Zürich, Zürich, Switzerland, R.L. Graham University of California at San Diego (UCSD), La Jolla, CA, USA, A.A. Ivanov Imperial College London, London, UK, G.O.H. Katona Hungarian Academy of Sciences, Budapest, Hungary, S. Klavzar University of Ljubljana, Ljubljana, Slovenia, C. Krattenthaler University of Vienna, Wien, Austria, M. Krivelevich Tel Aviv University, Tel Aviv, Israel, D. Král Charles University in Prague, Prague, Czech Republic, L. Lovász Microsoft Research, Redmond WA, USA, A. Lubotzky Hebrew University of Jerusalem, Jerusalem, Israel, A. Machi Università di Roma "La Sapienza", Rome, Italy, J. Nešetril Charles University, Praha 1, Czech Republic, A. Pasini Università degli Studi di Siena, Siena, Italy, N.M. Singhi TATA Inst. of Fundamental Res., Mumbai India, R.P. Stanley Massachusetts Institute of Technology (MIT), Cambridge, MA, USA, G.N. Sárközy Worcester Polytechnic Institute (WPI), Worcester, MA, USA, R.E. Tarjan Princeton University, Princeton, NJ, USA, C. Thomassen Danmarks Tekniske Universitet (DTU), Lyngby, Denmark, J. Tits Collège de France, Paris, France, X. Zhu Zhejiang Normal University, Jinhua City, China