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2. Feld, H., Zurmühlen, R., Leute, A., Benninghoven, A.: Unpublished work
3. Katakuse, I., Ichihara, T., Matsuo, T, Sakurai, T., Matsuda, H.: Int. J. Mass Spectrom. Ion Proc91, 99 (1989)
4. Sundqvist, B.U.R., Ariyaratne, A., Ens, W., Fenyö, D., Hedin, A., Hakansson, P., Jonsson, G., Widdiyasekera, S.: In: Ion formation from organic solids (IFOS IV). Benninghoven, A. (ed.) New York: John Wiley 1989
5. Feld, H., Zurmühlen, R., Leute, A., Benninghoven, A.: Anal. Chem. (submitted)