Affiliation: | (1) Department of Mathematics, Statistics and Computer Science, College of Basic Sciences and Humanities, G. B. Pant University of Agriculture and Technology, Pantnagar, 263 145, India;(2) Present address: Department of Management Sciences, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong;(3) Institute of Systems Science, Academy of Mathematics and Systems Science, Chinese Academy of Sciences, Beijing, 100080, China |