Trends in drug research : proceedings of the seventh Noordwijkerhout-Camerino Symposium, Noordwijkerhout, The Netherlands, 5-8 September 1989 / edited by V. ClaassenTrends in drug research : proceedings of the 9th Noordwijkerhout-Camerino Symposium, Noordwijkerhout, The Netherlands, 23-28 May 1993 / ed. by V. Claassen