@article{LJM_2003_13_a5,
     author = {N. Kehayopulu and M. Tsingelis},
     title = {A~note on semi-pseudoorders in semigroups},
     journal = {Lobachevskii journal of mathematics},
     pages = {51--55},
     publisher = {mathdoc},
     volume = {13},
     year = {2003},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/LJM_2003_13_a5/}
}