Al-Obaidi , H. N. ., and A. A. R. Al-Azawy. “An Investigation Tool for Analyzing Electrostatic Lenses”. Mustansiriyah Journal for Sciences and Education, vol. 17, no. 1, Sept. 2020, pp. 39-46, https://edumag.uomustansiriyah.edu.iq/index.php/mjse/article/view/206.