Vietnam Journal of Mathematics
Vietnam Journal of Mathematics > 2013 > 41 > 1 > 25-42
Vietnam Journal of Mathematics > 2015 > 43 > 1 > 121-130
Vietnam Journal of Mathematics > 2016 > 44 > 3 > 531-540
Vietnam Journal of Mathematics > 2013 > 41 > 1 > 25-42
Vietnam Journal of Mathematics > 2015 > 43 > 1 > 121-130
Vietnam Journal of Mathematics > 2016 > 44 > 3 > 531-540