Institution: | (1) A. Razmadze Mathematical Institute, Georgian Academy of Sciences, 1, Z. Rukhadze Str., 380093 Tbilisi, Republic of Georgia;(2) Department of Mathematics, Georgian Technical University, (99) 77, M. Kostava Str., 380075 Tbilisi, Republic of Georgia;(3) Department of Mechanics and Mathematics, Tbilisi State University, 2, University Str., 380043 Tbilisi, Republic of Georgia |