1. Solovjov, A.L., Habermeier, H.U., Haage, T.: Fluctuation conductivity in YBa2Cu3O7−y films of various oxygen content II. YBCO films with T c ≈ 80 K. Fiz. Nizk. Temp. 28, 144–156 (2002)
2. Greaves, C., Slater, P.R.: Nb and Ta substitutions in YBa2Cu3O7−x and related phases: Structural characterisation of La1.1Ba1.9Cu2.1M0.9O8(M =Nb, Ta). Physica C 161, 245–251 (1989)
3. Augieri, A., Petrisor, T.G., Celentano, L., Ciontea, V., Galluzzi, U., Gambardella, A., Mancini, A.: Rufoloni, Effect of Ca doping in YBCO superconducting thin films. Physica C 401, 320–324 (2004)
4. Varshney, D., Yogi, A., Dodiya, N., Mansuri, I.: Alkaline earth (Ca) and transition metal (Ni) doping on the transport properties of Y1−xCaxBa2(Cu1−yNiy)3O7−δ superconductors. J. Mod. Phys. 2, 922–927 (2011)
5. Celebi, S., Ozturk, A., Karaca, I., Kolemen, U.: The effect of potassium doping on resistive transitions and transport critical current of bulk YBCO high-T c superconductors. Turky J. Phy. 24, 567–576 (2000)