Berge's characterization of minimally imperfect graphs

Let $G$ be a finite simple graph. A minimally imperfect graph is a graph that is not perfect but whose proper induced subgraphs are all perfect. A hole is a chordless cycle of length at least $4$, and an odd hole is a hole with an odd number of vertices. Let $\bar G$ denote the complement of $G$. Berge's conjecture. The only minimally imperfect graphs are the odd holes and their complements.

This is an equivalent formulation of the Strong Perfect Graph Conjecture. It was proved by Lovász's Perfect Graph Theorem together with the later proof of the Strong Perfect Graph Conjecture by Chudnovsky, Robertson, Seymour and Thomas.