[1] Glivjak F., Kyš P., Plesník J.: On the extsnsion of graphs with a given diameter without superfluous edges. Mat. časop. 19 (1969), 92-101. MR 0302503

[2] Eгdös P.: Extremal problems in graph theory. Proceedings of tho Sуmposium held in Smolenice in June 1963, Publ. H. Czechoslovak Acad. Sc. Prague 1964, 29-36. MR 0180500

[3] Erdös P., Rénуi A., Sós V. T.: On a problem of graph theory. Studia Sci. Math. Hung. 1 (1966), 215-235. MR 0223262