Ding, Jingtao, et al. “Study on Dynamic Sorption Characteristics of Modified Biochars for Ammonium in Biogas Slurry”. International Journal of Agricultural and Biological Engineering, vol. 13, no. 1, Mar. 2020, pp. 234-40, https://ijabe.migration.pkpps06.publicknowledgeproject.org/index.php/ijabe/article/view/4697.