M. T. Jamil, J. Ahmad, S. H. Bukhari, and M. Saleem, Effect of Re and Tm-site on morphology structure and optical band gap of ReTmO3 (Re: La, Ce, Nd, Gd, Dy, Y and Tm: Fe, Cr) prepared by sol-gel method, Rev. Mex. Fís. 64, (2018).