Vuong, L. D. ., P. D. . Gio, and V. T. T. . Kieu. “Raman Scattering Spectra and Dielectric Relaxation Behavior of Pzt-Pzn-Pmnn Ceramics”. International Journal of Chemistry and Materials Research, vol. 2, no. 6, June 2014, pp. 48-55, https://archive.conscientiabeam.com/index.php/64/article/view/1830.