The embedding of an ordered semigroup in a simple one with identity. N. Kehayopulu; M. Tsingelis — 1996 Semigroup forum
On the decomposition of prime ideals of ordered semigroups into their N-classes. N. Kehayopulu; M. Tsingelis — 1993 Semigroup forum
On weakly commutative poe-semigroups. N. Kehayopulu; Kiriakuli P.; S. Hanumantha Rao; P. Lakshmi — 1990 Semigroup forum
A note on pseudocongruences in semigroups. Kehayopulu, N.; Tsingelis, M. — 2002 Lobachevskii Journal of Mathematics
A note on minimal and maximal ideals of ordered semigroups. Arslanov, M.; Kehayopulu, N. — 2002 Lobachevskii Journal of Mathematics
Bi-ideals in ordered semigroups and ordered groups. Kehayopulu, N.; Ponizovskij, J.S.; Tsingelis, M. — 1999 Zapiski Nauchnykh Seminarov POMI
Retract extensions of ordered sets. Kehayopulu, N.; Ponizovskij, J.S.; Shum, K.P. — 2005 Zapiski Nauchnykh Seminarov POMI