1. Interpol, Pharmaceutical Crime, http://www.interpol.int/Crime-areas/Pharmaceutical-crime/Operations/Operation-Pangea (accessed 16.12.11).
2. Characteristics, behaviors, and attitudes of men bypassing the healthcare system when obtaining phosphodiesterase type 5 inhibitors;Schnetzler;J. Sex. Med.,2010
3. Economic analysis of use of counterfeit drugs: health impairment risk of counterfeit phosphodiesterase type 5 inhibitor taken as an example;Sugita;Environ. Health Preventive Med.,2010
4. B.J. Venhuis, M.E. Zwaagstra, J.D.J.v.d. Berg, A.J.H.P.v. Riel, H.W.G. Wagenaar, K.v. Grootheest, D. Barends, D.d. Kaste, in: Illicit erectile dysfunction products in the Netherlands; a decade of trends and a 2007–2010 product update, RIVM rapport 370030003, National Institute for Public Health and the Environment, 2010, pp. 75.
5. Safety and efficacy of sildenafil citrate in the treatment of male erectile dysfunction;Goldenberg;Clin. Therap.,1998