@article{IVM_2003_9_a5,
     author = {N. Kehayopulu and M. Tsingelis},
     title = {Adjoining zero to ordered groupoid-semigroups},
     journal = {Izvesti\^a vys\v{s}ih u\v{c}ebnyh zavedenij. Matematika},
     pages = {28--35},
     publisher = {mathdoc},
     number = {9},
     year = {2003},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/IVM_2003_9_a5/}
}