“Univariate and Multivariate Optimization of Spectrophotometric Determination of Europium (III) in Pure Form and Synthetic Sample”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 27, no. 2, Apr. 2017, pp. 198-10, https://jih.uobaghdad.edu.iq/index.php/j/article/view/344.