1. Ore, O.: Diameters in graphs. J. Combin. Theory 5, 75–81 (1968)
2. West, D.B.: Introduction to Graph Theory. Prentice Hall Inc., Upper Saddle River (1996)
3. Zhou, T., Xu, J.M., Liu, J.: Extremal problems on diameter and average distance of graphs. J. Univ. Sci. Tech. China 34(4), 410–413 (2004). (in Chinese)