Li, Qiang, et al. “Effects of Urea Ammonia Pretreatment on the Batch Anaerobic Fermentation Efficiency of Corn Stovers”. International Journal of Agricultural and Biological Engineering, vol. 12, no. 4, Aug. 2019, pp. 169-73, https://ijabe.migration.pkpps03.publicknowledgeproject.org/index.php/ijabe/article/view/4835.