Amnah, R. ., and M. . Friska. “Effect of Activator on Levels of C, N, P and K Compost of Salak Sidimpuan Leaf Midrib”. Jurnal Online Pertanian Tropik, vol. 6, no. 3, Dec. 2019, pp. 342-7, doi:10.32734/jopt.v6i3.3164.