Affiliation: | 1. Department of Applied Mathematics, AGH University of Science and Technology, , Krakow, Poland;2. Department of Econometrics, Institute of Mathematics, Cracow University of Technology, , Krakow, Poland;3. Department of Mathematics and Statistics, University of Cyprus, , Cyprus;4. Department of Mathematics, University of California, , La Jolla, CA, 92093‐0112 USA |