RT Article T1 Research Methods for Illegal Drug Use in Hidden Populations - Summary Report of a European Invited Expert Meeting JF Journal of psychoactive drugs VO 26 IS 1 SP 89 OP 91 A2 Goor, L. A. M. ¬van de¬ A2 Garretsen, H. F. L. A2 Kaplan, C. A2 Korf, D. A2 Spruit, I. P. A2 Zwart, W. M. ¬de¬ LA English YR 1994 UL https://krimdok.uni-tuebingen.de/Record/1639492356 K1 Drogenbekämpfung DO 10.1080/02791072.1994.10472599