A. Khan, Y. B. Jun and M. Shabir
N-fuzzy quasi-ideals in ordered semigroups

we introduce the concept of N-fuzzy quasi-ideals in ordered semigroups and investigate the basic theorem of quasi-ideals of ordered semigroups in terms of N-fuzzy quasi-ideals. We characterize left (resp. right) regular and completely regular ordered semigroups in terms of N-fuzzy quasi-ideals. We define semiprime N-fuzzy quasi-ideals and characterize completely regular ordered semigroups in terms of semiprime N-fuzzy quasi-ideals. We provide characterizations of some semilattices of left and right simple semigroups in terms of N-fuzzy quasi-ideals.