Journal of Mathematics and Statistics 5 ( 4 ): 375 - 378 , 2009
Journal of Mathematics and Statistics 6 ( 3 ): 325 - 326 , 2010
Journal of Mathematics and Statistics 6 ( 3 ): 347 - 349 , 2010
Journal of Modern Mathematics and Statistics 5 ( 1 ): 30 - 32 , 2011