Spectra and energies of iterated line graphs of regular graphs. - Harishchandra S. Ramane; Hanumappa B. Walikar; Siddani Bhaskara Rao; B. Devadas Acharya; Prabhakar Ramrao Hampiholi; Sudhir R. Jog; Ivan Gutman (Appl. Math. Lett., 2005)