Basyirah Md Zin, Nur, et al. “Chemical Composition and Antioxidant Activity of Stingless Bee Propolis from Different Extraction Methods”. International Journal of Engineering & Technology, vol. 7, no. 4.43, Dec. 2018, pp. 90-95, https://doi.org/10.14419/ijet.v7i4.43.25825.