@article{MAN_1964__153_161117,
     author = {R. HALIN},
     title = {\"Uber einen {Satz} von {K.} {Wagner} zum {Vierfarbenproblem.}},
     journal = {Mathematische Annalen},
     pages = {47--62},
     publisher = {mathdoc},
     volume = {153},
     year = {1964},
     url = {http://geodesic.mathdoc.fr/item/MAN_1964__153_161117/}
}