Institution: | 1. University of North Carolina, Greensboro, Department of Mathematics and Statistics, UNC Greensboro, Greensboro, NC 27402, USA;2. University of West Bohemia, Department of Mathematics, University of West Bohemia, Univerzitní 22, 306 14 Plzeň, Czech Republic;3. Wake Forest University, Department of Mathematics, P.O. Box 7388, Winston Salem, NC 27109, USA |