1. Perfectly ordered graphs;Chvátal,1984
2. V. Chvátal and C. T. Hoang, On the P4-structure of perfect graphs. I. Even decompositions, Technical report SOCS 83.10, McGill University; J. Combin. Theory Ser. B, in press.
3. Normal hypergraphs and the perfect graph conjecture;Lovasz;Discrete Math.,1972