M. Murer, “Fluctuation-induced conductivity of polycrystalline Gd$_{1 - x}$Ce$_{x}$Ba$_{2}$Cu$_{3}$O$_{7 - \delta }$ superconductor”, Rev. Mex. Fís., vol. 58, no. 5 Sept-Oct, pp. 404–410, Jan. 2012.