@article{10_4153_CJM_1973_080_7,
     author = {Tutte, W. T.},
     title = {Chromatic {Sums} for {Rooted} {Planar} {Triangulations,} {III:} {The} {Case} \ensuremath{\lambda} = 3},
     journal = {Canadian journal of mathematics},
     pages = {780--790},
     year = {1973},
     volume = {25},
     number = {4},
     doi = {10.4153/CJM-1973-080-7},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1973-080-7/}
}