1. Onnes, H.K.: The Superconductivity of Mercury, Comm. Phys. Lab. Univ. Leiden. 122, 2 (1911)
2. Bardeen, J., Cooper, L.N., Schrieffer. J.R.: Theory of superconductivity. Phy. Rev. 108, 1175 (1957)
3. Bednorz, J.G., Müller, K.A.: Zeitschrift für. Physic B. 64, 189 (1986)
4. Zhao, Z., Chen, L., Cui, C., et al.: Kexue, Tongbao. Sci. Bull. 32, 522 (1987)
5. Cava, R.J., Takagi, H., Batiogg, B., et al.: Nature. 367, 146 (1994)