Piyavadee Srivichai, and Orathai Chavalparit. “OPTIMIZATION OF BIOGAS PRODUCTION FROM CO-DIGESTION OF WASTE ACTIVATED SLUDGE AND MODIFIED TAPIOCA STARCH SLUDGE”. GEOMATE Journal, vol. 18, no. 67, Mar. 2020, pp. 148-55, https://geomatejournal.com/geomate/article/view/505.