[1] V. Baláž, J. Koča, V. Kvasnička, M. Sekanina: Metric for graphs. Čas. Pěst. Mat. 111 (1986), no. 2, 431–433. MR 0871718

[2] V. Baláž, V. Kvasnička, J. Pospíchal: Dual approach for edge distance between graphs. Čas. Pěst. Mat. 114 (1989), no. 2, 155–159.

[3] M. A. Johnson: Relating metrics, lines and variables defined on the space of graphs. Proceedings of the Fifth International Conference on Graph Theory. Eds. Y. Alavi, G. Chartrand, L. Lesniak and C. Wall. John Wiley. New York (1985), 457–470. MR 0812683

[4] M. Šabo: On a maximal distance between graphs. Czech. Math. J. 41 (1991), . MR 1105441