1. UNODC, The challenge of new psychoactive substances. Global SMART Programme. March 2013. see https://www.unodc.org/unodc/en/commissions/CND/Mandate_Functions/Mandateand-Functions_Scheduling.html
2. United Nations Office on Drugs and Crime, World Drug Report 2017 (ISBN: 978-92-1-148291-1, eISBN: 978-92-1-060623-3, United Nations publication, Sales No. E.17.XI.6); available at https://www.unodc.org/wdr2017/field/Booklet_4_ATSNPS.pdf
3. UNODC, Understanding the synthetic drug market: the NPS factor, Global SMART Update vol 19, March 2018. available at http://www.unodc.org/documents/scientific/Global_Smart_Update_2018_Vol.19.pdf
4. European Drug Users at Risk from Illicit Fentanyls Mix;Pichini;Front. Pharmacol.,2017
5. available at http://www.emcdda.europa.eu/publications/implementation-reports/2016