Editing Strong perfect graph theorem (section)

==Statement==
A [[perfect graph]] is a graph in which, for every [[induced subgraph]], the size of the [[maximum clique]] equals the minimum number of colors in a [[graph coloring|coloring]] of the graph; perfect graphs include many well-known graph classes including the [[bipartite graph]]s, [[chordal graph]]s, and [[comparability graph]]s. In his 1961 and 1963 works defining for the first time this class of graphs, [[Claude Berge]] observed that it is impossible for a perfect graph to contain an odd hole, an induced subgraph in the form of an odd-length [[cycle graph]] of length five or more, because odd holes have clique number two and chromatic number three. Similarly, he observed that perfect graphs cannot contain odd antiholes, induced subgraphs [[complement graph|complementary]] to odd holes: an odd antihole with 2''k''&nbsp;+&nbsp;1 vertices has clique number ''k'' and chromatic number ''k''&nbsp;+&nbsp;1, which is again impossible for perfect graphs. The graphs having neither odd holes nor odd antiholes became known as the Berge graphs.

Berge conjectured that every Berge graph is perfect, or equivalently that the perfect graphs and the Berge graphs define the same class of graphs. This became known as the strong perfect graph conjecture, until its proof in 2002, when it was renamed the strong perfect graph theorem.