@article { author = {}, title = {Bulletin of the Iranian Mathematical Society}, journal = {Bulletin of the Iranian Mathematical Society}, volume = {42}, number = {1}, pages = {-}, year = {2016}, publisher = {Iranian Mathematical Society (IMS)}, issn = {1017-060X}, eissn = {1735-8515}, doi = {}, abstract = {}, keywords = {}, url = {http://bims.iranjournals.ir/article_734.html}, eprint = {http://bims.iranjournals.ir/article_734_188d7c020645c10b86eb8c134817cd73.pdf} }