Affiliation: | 1.Department of Mathematics, Informetrics Research Group, Ton Duc Thang University, Ho Chi Minh City, Vietnam ;2.Faculty of Mathematics & Statistics, Ton Duc Thang University, Ho Chi Minh City, Vietnam ;3.Academy of Romanian Scientists, 050094, Bucharest, Romania ;4.Department of Theoretical Mechanics, Technical University “Gheorghe Asachi” of Ia?i, Iasi, Romania ; |