NH, Harmiwati et al. Production of Biogas with Two-Stage Fermentation of Cow Dung-Palm Oil Mill Effluent. Walisongo Journal of Chemistry, [S. l.], v. 6, n. 1, p. 8–11, 2023. DOI: 10.21580/wjc.v6i1.13541. Disponível em: https://journal.walisongo.ac.id/index.php/wjc/article/view/13541. Acesso em: 5 dec. 2025.