This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.
Filip Edmund Gęstwicki
University of Warmia and Mazury in Olsztyn, The Department of Quantitative Methods, Faculty of Economics, M. Oczapowskiego 4, 10-710 Olsztyn, Poland
Ewa Wędrowska
Nicolaus Copernicus University in Toruń, The Department of Econometrics and Statistics, Faculty of Economic Sciences and Management, Gagarina 13 A, 87-100 Toruń, Poland