Khidhir, Ali H., and Mohammed A. Hameed. “Using Laser - Induced Breakdown Spectroscopy System to Determine the Fertility of Middle Iraqi Soil”. Iraqi Journal of Science, vol. 59, no. 4B, Nov. 2018, pp. 2012-9, https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/478.