Brandt, Simon D and King, Leslie A and Evans-Brown, Michael (2014) The new drug phenomenon. Drug Testing and Analysis, 6, (7-8), pp. 587-597. https://doi.org/10.1002/dta.1686.

King, Leslie A (2004) An overview of cannabis potency in Europe. Lisbon: European Monitoring Centre for Drugs and Drug Addiction.

European Monitoring Centre for Drugs and Drug Addiction. King, Leslie A and Sedefov, Roumen (2007) Early-warning system on new psychoactive substances: operating guidelines. Luxembourg: Office for Official Publications of the European Communities.