USDA National Nutrient Database for Standard Reference, 2009; Center for Science in the Public Interest, 2007; Journal of Analytical Toxicology, 2003.
Escohotado, Antonio; Ken Symington (1999). A Brief History of Drugs: From the Stone Age to the Stoned Age. Park Street Press. ISBN 0-89281- 826-3.
Frischknecht, P. M.; Ulmer-Dufek, Jindra; Baumann, Thomas W. (1986). "Purine formation in buds and developing leaflets of Coffea arabica: expression of an optimal defence strategy?". Phytochemistry (Journal of the Phytochemical Society of Europe and the Phytochemical Society of North America.) 25 (3): 613–6. doi:10.1016/0031-9422(86)88009-8
