@article{SF_1976__13_134203,
     author = {E. Valkema},
     title = {Syntaktische {Monoide} und {Hypercodes.}},
     journal = {Semigroup forum},
     pages = {119--126},
     publisher = {mathdoc},
     volume = {13},
     year = {1976},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/SF_1976__13_134203/}
}