@article{10_4153_CMB_1968_023_5,
     author = {Hedetniemi, Stephen},
     title = {On {Partitioning} {Planar} {Graphs}},
     journal = {Canadian mathematical bulletin},
     pages = {203--211},
     year = {1968},
     volume = {11},
     number = {2},
     doi = {10.4153/CMB-1968-023-5},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1968-023-5/}
}