Abraham, Manja D. and Kaal, Hendrien L. and Cohen, Peter DA. (2003) Licit and illicit drug use in Amsterdam, 1987 to 2001: developments of drugs use in Amsterdam, as measured in five population surveys between 1987 and 2001. Mets & Schilt : CEDRO, Universiteit van Amsterdam , Amsterdam. ISBN 90-5330-379-0