Natalina, et al. “The Used of Variuos Biomass Waste As Raw Material Biogass Production Using Cow Dung As Source of Microbe by Continuously-Anaerobic Fermentation on the 15 Liter Reactor”. Engineering And Technology Journal, vol. 9, no. 9, Sept. 2024, pp. 5060-4, doi:10.47191/etj/v9i09.09.