@article{CTGDC_2006__47_1_29_0,
     author = {Attal, Romain},
     title = {Combinatorial stacks and the four-color theorem},
     journal = {Cahiers de Topologie et G\'eom\'etrie Diff\'erentielle Cat\'egoriques},
     pages = {29--49},
     publisher = {Dunod \'editeur, publi\'e avec le concours du CNRS},
     volume = {47},
     number = {1},
     year = {2006},
     mrnumber = {2220060},
     zbl = {1107.18005},
     language = {en},
     url = {http://archive.numdam.org/item/CTGDC_2006__47_1_29_0/}
}