Cheng, Jihai, and Changan Tian. “Synthesis and Electrochemical Properties of BaCe0.8Gd0.2O3 Protonic Conductor”. Asian Journal of Chemistry, vol. 24, no. 9, May 2012, pp. 4068-70, https://asianpubs.org/index.php/ajchem/article/view/9546.