Sihombing, Junifa Layla, et al. “Unveiling ZrO2 Natural Zeolite Catalytic Performance on Hydrocracking Palm Oil Mill Effluent Residue”. Jurnal Pendidikan Kimia, vol. 15, no. 2, Aug. 2023, pp. 100-1, doi:10.24114/jpkim.v15i2.43324.