1. C. Berge, Hypergraphs — Combinatorics of Finite Sets, North-Holland, Amsterdam, 1989.
2. Precoloring extension, I. Interval graphs;Biró;Discrete Math.,1992
3. Steiner triple systems with small maximal independent sets;de Brandes;Ars Combin.,1984
4. Mixed interval hypergraphs;Bulgaru;Discrete Appl. Math.,1997
5. On chromatic number of graphs and set systems;Erdős;Acta Math. Acad. Sci. Hungar.,1966