Xiao, Maohua, et al. “Design and Experiment of Fuzzy-PID Based Tillage Depth Control System for a Self-Propelled Electric Tiller”. International Journal of Agricultural and Biological Engineering, vol. 16, no. 4, Oct. 2023, pp. 116-25, https://ijabe.migration.pkpps03.publicknowledgeproject.org/index.php/ijabe/article/view/8116.