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.
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.