@article{SF_1979__17_134333,
     author = {K. Todorov},
     title = {Die...-Klassen der endlichen symmetrischen {Halbgruppen} und ihre {M\"achtigkeiten.}},
     journal = {Semigroup forum},
     pages = {387--388},
     publisher = {mathdoc},
     volume = {17},
     year = {1979},
     zbl = {0433.20044},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__17_134333/}
}