1. Kalso Eija. (2004): Improving opoid effectiveness: from ideas to evidence. European Journal of Pain., 9, 131–135.
2. Radulovic D., Vladimirov S. (2005): Farmaceutska hemija I deo, Grafopan, Beograd.
3. Shipton E. (2000): Tramadol — Present and future. Anaesth Intensive Care., 28, 4
4. Frink M.C., Hennies H.H., Engleberger W., Haurand M., Wilffert B. (1996) Influence of tramadol on neurotransmitter system of the rat brain. Arzneim.-Forsch., 46, 1029–1036
5. Mikov M., Fawcett J.P. (eds), (2007): Bile Acids, Medishet Publisher, Geneva.