Suarin, N. A. S., Chia, K. S., & Mohamad Fuzi, S. F. Z. (2018). A Portable in-situ Near-infrared LEDs-based Soil Nitrogen Sensor. International Journal of Integrated Engineering, 10(4). https://publisher.uthm.edu.my/ojs/index.php/ijie/article/view/2316