Kim, Sung-Min, et al. “Effect of Additional Heat Treatment of a Pd-Au-Ag Metal-Ceramic Alloy on Hardness Change During Simulated Porcelain Firing”. International Journal of Engineering & Technology, vol. 8, no. 1.4, Jan. 2019, pp. 183-90, https://doi.org/10.14419/ijet.v8i1.4.25145.