[1] N. Kehayopulu, Xiangyun Xie and M. Tsingelis, A characterization of prime and semiprime ideals of groupoids in terms of fuzzy subsets, Soochow J. Math. 27, no. 2 (2001), 139–144.
[2] N. Kehayopulu and M. Tsingelis, Fuzzy sets in ordered groupoids, Semigroup Forum 65, no. 1 (2002), 128–132.
[3] Y. Feng, p-fuzzy quasi-hypergroups obtained from fuzzy binary relations, J. Dis-crete Math. Sci. and Cryptogr. 13, no. 3 (2010), 201–208.
[4] Y. Feng, p-fuzzy hypergroups and p-fuzzy join spaces obtained from p-fuzzy hy-pergraphs, Ital. J. Pure Appl. Math. 27 (2010), 273–280.
[5] Y. Feng, Hypergraph superlattice and p-fuzzy hypergraph superlattice, Fuzzy Sets, Rough Sets and Multivalued Operations and Applications 1, no. 2 (2009), 163–171.