1. United Nations Office on Drugs and Crime. World Drug Report. 2018. Available at https://www.unodc.org/wdr2018/prelaunch/WDR18_Booklet_1_EXSUM.pdf (accessed March 2019).
2. NHS. Statistics on drug misuse: England. 2018. Available at https://digital.nhs.uk/data-and-information/publications/statistical/statistics-on-drug-misuse/2018 (accessed March 2019).
3. National Institute on Drug Abuse. Trends and Statistics. 2017. Available at https://www.drugabuse.gov/related-topics/trends-statistics (accessed March 2019).
4. The Canyon Treatment Center. Nick names and street names for heroin. Available at https://thecanyonmalibu.com/heroin-rehab/street-names/ (accessed March 2019).
5. Drugs and Lactation Database. Heroin. 2018. Available at https://www.ncbi.nlm.nih.gov/books/NBK500783/ (accessed March 2019).