Wang, C.S., Jung, G.Y., Hua, Y.L., Pearson, C., Bryce, M.R., Petty, M.C., Batsanov, A.S., Goeta, A.E., Howard, J.A.K., "An efficient pyridine- and oxadiazole-containing hole-blocking material far organic light-emitting diodes: Synthesis, crystal structure, and device performance", Chemistry of Materials, 2001