Cornil, J.; Gruhn, N.E.; dos Santos, D.A.; Malagoli, M.; Lee, P.A.; Barlow, S.; Thayumanavan, S.; Marder, S.R.; Armstrong, N.R.; Brédas, J.L. “Joint Experimental and Theoretical Characterization of the Electronic Structure of 4,4′-Bis(N-m-tolyl-N-phenylamino)biphenyl (TPD) and Substituted Derivatives” J. Phys. Chem. A. 2001, 105, 5206-5211. (DOI: 10.1021/jp003142o)