@article{MASLO_1969_19_4_a8,
     author = {Fabrici, Imrich},
     title = {Classes of {Regularity} in {Semigroups}},
     journal = {Mathematica slovaca},
     pages = {299--304},
     year = {1969},
     volume = {19},
     number = {4},
     mrnumber = {0306365},
     zbl = {0186.31202},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/MASLO_1969_19_4_a8/}
}