Liu, Jun, Haotian Cai, Jie Pi, and Liye Zhao. “Development of the Portable Device for the Determination of Nitrate-Nitrogen Contents in Soil”. International Journal of Agricultural and Biological Engineering 18, no. 4 (August 21, 2025): 216–228. Accessed January 27, 2026. https://ijabe.org/index.php/ijabe/article/view/8820.