@article{MM2_1974__14_154292,
     author = {K. Braun and M. Kretz and B. Walter},
     title = {Die chromatischen polynome {Unterringfreier} {Graphen.}},
     journal = {Manuscripta mathematica},
     pages = {223--234},
     publisher = {mathdoc},
     volume = {14},
     year = {1974},
     zbl = {0293.05113},
     url = {http://geodesic.mathdoc.fr/item/MM2_1974__14_154292/}
}