Utami, S R, C Agustina, K S Wicaksono, B D Prasojo, and H Hanifa. 2017. “Utilization of Locally Available Organic Matter to Improve Chemical Properties of Pyroclastic Materials from Mt. Kelud of East Java”. Journal of Degraded and Mining Lands Management 4 (2). Malang, Indonesia:717-21. https://doi.org/10.15243/jdmlm.2017.042.717.