@article{JRAM_1974__0268_0269_151465,
     author = {G.A. Dirac and B. Toft and B. A. Sorensen},
     title = {An extremal result for graphs with an application to their colourings.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {216--221},
     publisher = {mathdoc},
     volume = {0268_0269},
     year = {1974},
     zbl = {0298.05117},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1974__0268_0269_151465/}
}