“Potentiometric Analysis of Samarium Ion in Aqueous Solution Employing Selective Electrode Based on Crown Ethers - Samarium Picrate Complexes in a PVC Membrane”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 19, no. 3, Dec. 2017, pp. 117-133A, https://jih.uobaghdad.edu.iq/index.php/j/article/view/1653.