Zhangliu, Du, et al. “Soil Physical Quality As Influenced by Long-Term Fertilizer Management under an Intensive Cropping System”. International Journal of Agricultural and Biological Engineering, vol. 2, no. 1, Mar. 2009, pp. 19-27, https://ijabe.migration.pkpps06.publicknowledgeproject.org/index.php/ijabe/article/view/56.