Yan, B. “A Study on Phase Equilibria in the CaO-Al2O3-SiO2-‘Nb2O5’(5 Mass Pct) System in Reducing Atmosphere”. Journal of Mining and Metallurgy, Section B: Metallurgy, Vol. 49, no. 2, July 2013, p. 145, https://aseestant.ceon.rs/index.php/jmm/article/view/2438.