Anrokhi, M. S., O. B. Abdillah, F. A. Noor, P. Fitriani, and F. Iskandar. “Electrochemical Study of Demineralized Bituminous Coal by Alkali-Acid Leaching Assisted Low-Frequency Ultrasonication”. ITB Graduate School Conference, vol. 3, no. 1, Oct. 2023, pp. 868-75, https://gcs.itb.ac.id/proceeding-igsc/index.php/igsc/article/view/200.