Chanathaworn, J., and K. Phumivanichakit. “Experimental co-digestion of carbon rich source and earthworm bedding wastewater to improve Bio-methane potential using experimental design”. Journal of Renewable Energy and Smart Grid Technology, vol. 13, no. 2, June 2018, https://ph01.tci-thaijo.org/index.php/RAST/article/view/78730.