Affiliation: | 1. The West University of Timi?oara, Faculty of Mathematics and C.S., Department of Mathematics, B-dl. Vasile Parvan, No. 4, 300223-Timi?oara, Romania;2. “Politehnica” University of Timi?oara, Department of Mathematics, Pia?a Victoriei nr. 2, 300006-Timi?oara, Romania |