@article{MZ_1959__72_183624,
     author = {Gert Sabidussi},
     title = {Graph {Multiplication.}},
     journal = {Mathematische Zeitschrift},
     pages = {446--457},
     publisher = {mathdoc},
     volume = {72},
     year = {1959},
     zbl = {0093.37603},
     url = {http://geodesic.mathdoc.fr/item/MZ_1959__72_183624/}
}