San Thy, Buntha P, Vanvuth T, Preston T R, Duong Nguyen Khang, Soukanh K, Boualong Phouthone, Choke Mikled and Sopharoek N 2005: Effect of length: diameter ratio in polyethylene biodigesters on gas production and effluent composition. Livestock Research for Rural Development. Volume 17, Article #120. Retrieved , from http://www.lrrd.org/lrrd17/11/sant17120.htm