1. Dense neighbourhoods and Turán's theorem;Bollobás;J. Combin. Theory Ser. B,1981
2. On the graph-theorem of Turán (Hungarian);Erdös;Mat. Lapok,1970
3. Some recent progress on extremal problems in graph theory;Erdös,1975
4. P. Erdös and V. T. Sós, preprint.
5. An extremal problem in graph theory (Hungarian);Turán;Mat. Fiz. Lapok,1941