@article { author = {}, title = {Bulletin of the Iranian Mathematical Society}, journal = {Bulletin of the Iranian Mathematical Society}, volume = {43}, number = {2}, pages = {-}, year = {2017}, publisher = {Iranian Mathematical Society (IMS)}, issn = {1017-060X}, eissn = {1735-8515}, doi = {}, abstract = {}, keywords = {}, url = {http://bims.iranjournals.ir/article_1119.html}, eprint = {http://bims.iranjournals.ir/article_1119_8b433c3d08c8d87751f6a1cb1f063aef.pdf} }