Affiliation: | 1. Faculty of Mathematics , University “Al.I. Cuza,” and Institute of Mathematics “Octav Mayer,” , Ia?i, Romania sanita@uaic.ro;3. Faculty of Mathematics , University “Al.I. Cuza,” , Ia?i, Romania;4. Department of Mathematics and Computer Science, “Gr.T. Popa” , University of Medicine-Pharmacy , Ia?i, Romania |