L. Beineke: Derived graphs and digraphs. In Sachs/Voss/Walther 1968, 17-33. L. Chang: The uniqueness and nonuniqueness of the triangular association scheme. Sci. Record 3 (1959), 604-613. A. Hoffman: On the uniqueness of the triangular association scheme. Ann. Math. Stat. 31 (1960), 492-497. A. Hoffman: On the exceptional case in a characterization of the arcs of complete graphs. IMB J. Res. Devel. 4 (1960), 487-496. A. Hoffman: On the line-graph of the complete bipartite graph. Ann. Math. Stat. 35 (1964), 883-885. H. Jung: Zu einem Isomorphiesatz von Whitney fu''r Graphen. Math. Ann. 164 (1966), 270-271. J. Krausz: Demonstration nouvelle d'une theoreme de Whitney sur les reseaux. Mat. Fiz. Lapok 50 (1943), 75-89. V. Menon: On repeated interchange graphs. Am. Math. Monthly 13 (1966), 986-989. J. Moon: On the line graph of the complete bigraph. Ann. Math. Stat. 34 (1963), 664-667. A. van Rooij/H. Wilf: The interchange graphs of a finte graph. Acta Math. Ac. Sci. Hung. 16 (1965), 263-269. G. Sabidussi: Graph derivatives. Math. Zeitschr. 76 (1961), 385-401. Horst Sachs/H. Voss/H. Walther (ed.): Beitra''ge zur Graphentheorie. Teubner Leipzig 1968. S. Shrikhande: On a characterization of the triangular association scheme. Ann. Math. Stat. 30 (1959), 39-47. Hassler Whitney: Congruent graphs and the connectivity of graphs. Am. J. Math. 54 (1932), 150-168.