N. MULYONO, A. MAAS, B. H. PURWANTO, and P. SUDIRA, “Short Communication: Volcanic ash utilization as planting medium of curly lettuce with charcoal husk and urban waste compost as soil amendment”, Asian J Agric, vol. 2, no. 2, pp. 39–43, Nov. 2018, doi: 10.13057/asianjagric/g020201.