@article{SF_1982__25_134560,
     author = {F.W. Roush and K.H. Kim and L.G. Makar-Limanov},
     title = {Graph {Monoids.}},
     journal = {Semigroup forum},
     pages = {1--8},
     publisher = {mathdoc},
     volume = {25},
     year = {1982},
     zbl = {0497.05060},
     url = {http://geodesic.mathdoc.fr/item/SF_1982__25_134560/}
}