@article{BSMF_1925__53__42_1,
     author = {Errera, A.},
     title = {Une contribution au probl\`eme des quatre couleurs},
     journal = {Bulletin de la Soci\'et\'e Math\'ematique de France},
     pages = {42--55},
     publisher = {Soci\'et\'e math\'ematique de France},
     volume = {53},
     year = {1925},
     doi = {10.24033/bsmf.1080},
     language = {fr},
     url = {http://www.numdam.org/articles/10.24033/bsmf.1080/}
}