Institution: | 1. Institute of Mathematics and Computer Science, Wroc?aw University of Technology, ul. Wybrze?e Wyspiańskiego 27, 50-370 Wroc?aw, Poland;2. Institute of Mathematics, Polish Academy of Sciences, ul. ?niadeckich 8, 00-976 Warszawa, Poland;3. LAREMA, Université d’Angers, 2 Bd Lavoisier, 49045 Angers cedex 1, France |