Gennaro, M. C.; Abrigo, C. (1992). «Caffeine and theobromine in coffee, tea and cola-beverages or any other fizzy drinks». Fresenius' Journal of Analytical Chemistry. 343 (6): 523–525. ISSN0937-0633. doi:10.1007/BF00322162
Gennaro, M. C.; Abrigo, C. (1992). «Caffeine and theobromine in coffee, tea and cola-beverages or any other fizzy drinks». Fresenius' Journal of Analytical Chemistry. 343 (6): 523–525. ISSN0937-0633. doi:10.1007/BF00322162