Mumpuni, Irna Diah, et al. “Activation of Oil Palm Empty Bunches With Hydrochloride Acid & Phosphoric Acid and Characterization Based SNI No. 06-3730-1995”. Sains Natural: Journal of Biology and Chemistry, vol. 11, no. 1, Apr. 2021, pp. 16-23, doi:10.31938/jsn.v11i1.291.