Laksmi, P. W., S. Setiati, T. Z. Tamin, P. Soewondo, W. Rochmah, N. Nafrialdi, and J. Prihartono. “Effect of Metformin on Handgrip Strength, Gait Speed, Myostatin Serum Level, and Health-Related Quality of Life: A Double Blind Randomized Controlled Trial Among Non-Diabetic Pre-Frail Elderly Patients”. Acta Medica Indonesiana, vol. 49, no. 2, Aug. 2017, p. 118, https://actamedindones.org/index.php/ijim/article/view/330.