Hussain, Khalid, Zhari Ismail, and Amirin Sadikun. 2010. “High Performance Thin-Layer Chromatography Method for Quantification of Betulinic Acid in Extracts of Leaves of Orthosiphon Stamineus Benth”. Asian Journal of Chemistry 23 (3):977-79. https://asianpubs.org/index.php/ajchem/article/view/16072.