Purwoko, P., Romli, M., Suprihatin, S., & Haditjaroko, L. (2015). Alkaline Pretreatment of Sorghum Stalk and Co-Digestion with Sludge for Biogas Production. International Journal of Sciences: Basic and Applied Research (IJSBAR), 24(1), 15-23. https://www.gssrr.org/JournalOfBasicAndApplied/article/view/4357