Walter Riess Heike Riel Tilman Beierlein Wolfgang Brütting Peter Müller Paul F. Seidler Influence of trapped and interfacial charges in organic multilayer light-emitting devices. 77-88 2001 45 IBM Journal of Research and Development 1 http://www.research.ibm.com/journal/rd/451/riess.html db/journals/ibmrd/ibmrd45.html#RiessRBBMS01