1. Abel-Ollo, K., Talu, A., Vals, K., Vorobjov, S., Paimre, M., Ahven, A., et al. (2007) National Report (2006 data) to the EMCDDA by the REITOX National Focal Point. Estonia. New developments and trends and in-depth information on selected issues. Available at: http://www.emcdda.europa.eu/system/files/publications/949/NR2007Estonia.pdf (accessed 15 October 2019).
2. Abel-Ollo, K.Fentanyl overdose deaths emergency and response in Estonia. Lisbon Addictions2019, Lisbon, Portugal, October 24, 2019. Available at: https://www.lisbonaddictions.eu/lisbon-addictions-2019/presentations/fentanyl-overdose-deaths-emergency-and-response-estonia (accessed October 15, 2019).
3. Scoping studies: towards a methodological framework;Arksey;Int J Soc Res Methodol,2005
4. Ashilevi, J. (2016). AASTA KÕIGE UNCOOL'IM RAAMAT [The most uncool book of the year]. Müürileht 2016; September 19. Available at: https://www.muurileht.ee/aasta-koige-uncoolim-raamat/ (accessed on 19 December 2019).
5. A deadly trend in fentanyl fatalities (England, 1998-2017);Claridge;Br J Clin Pharmacol,2019