@article{MOMA_1972__76_177577,
     author = {Wilfried Imrich and W. D\"orfler},
     title = {Das lexikographische {Produkt} gerichteter {Graphen.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {21--30},
     publisher = {mathdoc},
     volume = {76},
     year = {1972},
     zbl = {0234.05109},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1972__76_177577/}
}