Ahmed, Huda Yahya, and Munaf Yousif Hmood. “Comparison of Some Semi-Parametric Methods in Partial Linear Single-Index Model”. Journal of Economics and Administrative Sciences 27, no. 130 (December 1, 2021): 170–184. Accessed May 20, 2022. https://jeasiq.uobaghdad.edu.iq/index.php/JEASIQ/article/view/2207.