@article{EUG_1993_38_a17,
     author = {Niovi Kehayopulu and  Michael Tsingelis},
     title = {The {Ideal} extensions of ordered semigroups},
     journal = {E\ensuremath{\upsilon}\ensuremath{\kappa}\ensuremath{\lambda}\ensuremath{\varepsilon}\ensuremath{\acute\iota}\ensuremath{\delta}\ensuremath{\eta}\ensuremath{\varsigma} \ensuremath{\Gamma}},
     pages = {89--93},
     year = {1993},
     volume = {38},
     language = {gr},
     url = {http://geodesic.mathdoc.fr/item/EUG_1993_38_a17/}
}