Kristianingrum, S. et al. 2016. MODIFICATION OF KELUD VOLCANIC ASH 2014 AS SELECTIVE ADSORBENT MATERIAL FOR COPPER(II) METAL ION. Jurnal Sains Dasar. 5, 1 (Apr. 2016), 7–16. DOI:https://doi.org/10.21831/jsd.v5i1.12659.