Zhengjun, Guan, et al. “Two-Phase Anaerobic Co-Digestion of Dairy Manure With Swine Manure”. International Journal of Agricultural and Biological Engineering, vol. 9, no. 2, Mar. 2016, pp. 146-52, https://ijabe.migration.pkpps03.publicknowledgeproject.org/index.php/ijabe/article/view/1637.