@article{ZNSL_1999_265_a13,
     author = {N. Kehayopulu and I. S. Ponizovskii and M. Tsingelis},
     title = {Note on bi-ideals in ordered semigroups and in ordered groups},
     journal = {Zapiski Nauchnykh Seminarov POMI},
     pages = {198--201},
     publisher = {mathdoc},
     volume = {265},
     year = {1999},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/ZNSL_1999_265_a13/}
}