Sung Lim, Chang. “Synthesis and Spectroscopic Properties of Superparamagnetic Iron Oxide Nanoparticle CaWO4:Er3+, Yb3+ Composites by Microwave-Assisted Metathetic Method”. Asian Journal of Chemistry, vol. 26, no. 5, Mar. 2014, pp. 1297-00, doi:10.14233/ajchem.2014.17213.