Institution: | 1. Department of Mathematics and Statistics, Loyola University Chicago, 1032 W. Sheridan Road, Chicago, IL 60660, USA;2. Department of Mathematics, University of Craiova, 200585 Craiova, Romania;3. Research group of the project PN-II-ID-PCE-2012-4-0021, “Simion Stoilow” Institute of Mathematics of the Romanian Academy, P.O. Box 1-764, 014700 Bucharest, Romania |