Han, Nguyen, et al. “Effect of ExtractionConditions on Polyphenol Content and Antioxidant Activityof the Extract from Gynura Procumbens(Lour) Merr. Leaves”. Vietnam Journal of Agricultural Sciences, vol. 14, no. 8, Aug. 2024, pp. 1248-60, http://testtapchi.vnua.edu.vn/index.php/vjasvn/article/view/1433.