@article{SF_1979__18_134349,
     author = {H. Grassmann},
     title = {On factor {S-sets} of monoids modulo submonoids.},
     journal = {Semigroup forum},
     pages = {163--172},
     publisher = {mathdoc},
     volume = {18},
     year = {1979},
     zbl = {0419.20049},
     url = {http://geodesic.mathdoc.fr/item/SF_1979__18_134349/}
}