T. Damaiyanti, M. A. . Nasution, H. M. Nasution, and R. Yuniarti, “Determination of Caffeine Levels from Robusta Coffee Leaf Extract (Coffea canephora Pierre ex A. Froehner) and Arabica Coffee Leave (Coffea arabica L.) with High-Performance Liquid Chromatography Method”, JPS, vol. 6, no. 4, pp. 1544–1552, Sep. 2023.