Affiliation: | 1.Department of Mathematics, Oregon State University, Corvallis, OR, 97331, USA ;2.Institute of Mathematics, Academy of Sciences of Tajikistan, Ul. Ainy 299A, 734063, Dushanbe, Tajikistan ;3.Faculty of Education and Faculty of Mathematics and Physics, University of Ljubljana, Kardeljeva pl. 16, Ljubljana, 1000, Slovenia ;4.Department of Physics, Informatics and Mathematics, University of Modena and Reggio E, via Campi 213/B, 41125, Modena, Italy ; |