@article{GDZPPN002300060,
title = {Homomorphies\"atze f\"ur Graphen.},
journal = {Mathematische Annalen},
volume = {179},
year = {1968},
pages = {154-168},
zbl = {0165.57401},
url = {http://dml.mathdoc.fr/item/GDZPPN002300060}
}
MADER, W. Homomorphiesätze für Graphen.. Mathematische Annalen, Tome 179 (1968) pp. 154-168. http://gdmltest.u-ga.fr/item/GDZPPN002300060/