L. Pourkarimi, M.A. Yaghoobi and M. Mashinchi
Applied Mathematical Modelling 35 ( 1 ): 346 - 365 , 2011
V. Amirzadeh, M. Mashinchi and M.A. Yaghoobi
Journal of Mathematics and Statistics 4 ( 1 ): 26 - 31 , 2008