Affiliation: | 1. Faculty of Mathematics, University “Al. I. Cuza”, Ia?i, 700506, Bd. Carol I, no. 11, Romania;2. Department of Mathematics and Computer Science, University Transilvania of Bra?ov, Bra?ov 500091, Str. Iuliu Maniu 50, Romania;3. Department of Applied Mathematics, University of Craiova, Craiova, 200585, Str. Al. Cuza, no 13, Romania |