Weaver, Tim and Hart, Jo and Fehler, Jeffrey and Metrebian, Nicky and D'Agostino, Tony and Benn, Piers (2007) Are contingency management principles being implemented in drug treatment in England? London: National Treatment Agency for Substance Misuse.

Stimson, Gerry V and Metrebian, Nicky (2003) Prescribing heroin: what is the evidence? York: Joseph Rowntree Foundation .