Difference of Acidic Adding Effect in Ethanol Extraction of White Mulberry Stem Bark (Morus alba) and DPP-4 Inhibiting Activity Screening for Identifying its Antidiabetic Potential, Agusfina, Muhajri, Saputri Fadlina Chany, Sakti Aditya Sindu, and Mun?im Abdul , Pharmacognosy Journal, July 2019, Volume 11, Issue 4, p.790-795, (2019)