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Cécile Dartyge
Institut Elie Cartan, Université de Lorraine, B. P. 239 54506Vandoeuvre-lès-Nancy Cedex, France
Katalin Gyarmati
Eötvös Loránd University, Budapest, Hungary Institute of Mathematics, Department of Algebra and Number Theory and MTA-ELTE Geometric and Algebraic Combinatorics Research Group Pázmány Péter sétány 1/C H-1117Budapest, Hungary
András Sárközy
Eötvös Loránd University, Budapest, Hungary Institute of Mathematics, Department of Algebra and Number Theory and MTA-ELTE Geometric and Algebraic Combinatorics Research Group Pázmány Péter sétány 1/C H-1117Budapest, Hungary