@article{VM_2010_12_2_a2,
     author = {Patrick Labarque},
     title = {Blueprint for a classic proof of the 4 colour theorem},
     journal = {Visual Mathematics},
     publisher = {mathdoc},
     volume = {12},
     number = {2},
     year = {2010},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/VM_2010_12_2_a2/}
}