Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X Articles in Press 2011 05 25 Application of fundamental relations on n-ary polygroups en Bijan Davvaz Yazd University Saeed Mirvakili Payame Noor University 2011 05 24 Hypergroup polygroup $n$-ary hypergroup $n$-ary polygroup fundamental relation