Bempong DK, Houghton PJ, Steadman K (1993). "The xanthine content of guarana and its preparations". Int. J. Pharmacog. 31 (3): 175–81. doi:10.3109/13880209309082937. ISSN0925-1618.
Ashihara H, Sano H, Crozier A (February 2008). "Caffeine and related purine alkaloids: biosynthesis, catabolism, function and genetic engineering". Phytochemistry. 69 (4): 841–56. doi:10.1016/j.phytochem.2007.10.029. PMID18068204.
nih.gov
pubmed.ncbi.nlm.nih.gov
Ashihara H, Sano H, Crozier A (February 2008). "Caffeine and related purine alkaloids: biosynthesis, catabolism, function and genetic engineering". Phytochemistry. 69 (4): 841–56. doi:10.1016/j.phytochem.2007.10.029. PMID18068204.
worldcat.org
Bempong DK, Houghton PJ, Steadman K (1993). "The xanthine content of guarana and its preparations". Int. J. Pharmacog. 31 (3): 175–81. doi:10.3109/13880209309082937. ISSN0925-1618.