Gurning, K.; Lumbangaol, S.; Situmorang, R. F. R.; Silaban, S. Determination of Phenolic Contents and Antioxidant Activity Test of Ethanol Extract of Sirih Merah (Piper Crocatum Ruiz & Pav.) Leaves Using the DPPH Method. J.Pendidik.Kim 2021, 13, 137-142.