Caojun, Huang, Zhao Jing, Zhao Chen, Li Boshi, and Xin Dekui. 2015. “BeiDou-GPS Integrated Dual-System With Multi-Satellites for Positioning and Navigating Farm Vehicles”. International Journal of Agricultural and Biological Engineering 8 (5). Beijing, China:79-85. https://ijabe.org/index.php/ijabe/article/view/1400.