How return sludge increase biogas production from cow manure?Ambar Pertiwiningrum, Ratih Kusuma Wardani, Joko Wintoko, Rachmawan Budiarto, Margaretha Arnita Wuri and Misri GozanE3S Web Conf., 181 (2020) 01006DOI: https://doi.org/10.1051/e3sconf/202018101006
