@article{10_4153_CMB_1961_019_4,
     author = {Tutte, W.T.},
     title = {On the {Colourings} of {Graphs}},
     journal = {Canadian mathematical bulletin},
     pages = {157--160},
     year = {1961},
     volume = {4},
     number = {2},
     doi = {10.4153/CMB-1961-019-4},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1961-019-4/}
}