1. J.R. Gavaler Appl. Phys. Lett.23, 480 (1973)
2. M.K. Wu, J.R. Ashburn, C.J. Torng, P.H. Hor, R.L. Meng, L. Gao, Z.J. Huang, Y.Q. Wang, C.W. Chu: Phys. Rev. Lett.58, 908 (1987)
3. See, for example, M.A. Beno, L. Soderholm, D.W. Capone, D.G. Hinks, J.D. Jorgensen, J.D. Grace, I.K. Schuller, C.U. Segre, K. Zhang: Appl. Phys. Lett.51, 57 (1987)
4. See, for example, M.B. Maple, Y. Dalichaouch, J.M. Ferreira, R.R. Hake, B.W. Lee, J.J. Neumeier, M.S. Torikachvili, K.N. Yang, H. Zhou, r.P. Guertin, M.V. Kuric: to appear in ?Proceedings of the Yamada Conference XVIII on Superconductivity in Highly Correlated Fermion Systems?, Sendai, Japan, Aug. 31?Sept.3, 1987, and references cited therein
5. J.G. Bednorz, K.A. Müller: Z. Physik B64, 189 (1986)