Abd Malek, Sri Nurestri, Halijah Ibrahim, Hong Sok Lai, Lee Guan Serm, Chan Kam Seng, and Nor Azah Mohd. Ali. 2005. “The Essential Oils of Zingiber Officinale Variants”. Malaysian Journal of Science 24 (2):37-43. https://samudera.um.edu.my/index.php/MJS/article/view/8306.