%0 Journal Article %T Bulletin of the Iranian Mathematical Society %J Bulletin of the Iranian Mathematical Society %I Iranian Mathematical Society (IMS) %Z 1017-060X %D 2015 %\ 12/01/2015 %V 41 %N 6 %P - %! Bulletin of the Iranian Mathematical Society %R %X %U http://bims.iranjournals.ir/article_693_aebe6388c6767ba0888bc8c66b822047.pdf