@article{JRAM_1974__0268_0269_151457,
     author = {G.A. Dirac},
     title = {The number of edges in critical graphs.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {150--164},
     publisher = {mathdoc},
     volume = {0268_0269},
     year = {1974},
     zbl = {0298.05119},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1974__0268_0269_151457/}
}