Abd Malek, S. N., H. Ibrahim, H. Sok Lai, L. Guan Serm, C. Kam Seng, and N. A. M. Ali. “The Essential Oils of Zingiber Officinale Variants”. Malaysian Journal of Science, vol. 24, no. 2, Aug. 2005, pp. 37-43, https://samudera.um.edu.my/index.php/MJS/article/view/8306.