Bull-free Berge graphs are perfect
- Cite this article as:
- Chvátal, V. & Sbihi, N. Graphs and Combinatorics (1987) 3: 127. doi:10.1007/BF01788536
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Abull is the (self-complementary) graph with verticesa, b, c, d, e and edgesab, ac, bc, bd, ce; a graphG is calledBerge if neitherG not its complement contains a chordless cycle whose length is odd and at least five. We prove that bull-free Berge graphs are perfect; a part of our argument relies on a new property of minimal imperfect graphs.