* Carlson M, Thompson RD: Liquid chromatographic determination of methylxanthines and catechins in herbal preparations containing guarana. J AOAC Int, 81, 691-701, 1998 | * Carlson M, Thompson RD: Liquid chromatographic determination of methylxanthines and catechins in herbal preparations containing guarana. J AOAC Int, 81, 691-701, 1998 |