1. Wu, M.K., Ashburn, J.R., Torng, C.J., Hor, P.H., Meng, R.L., Gao, L., Huang, Z.J., Wang, Y.Q., Chu, C.W.: Phys. Rev. Lett.58, 908 (1987)
2. Chu, C.W.: (preprint)
3. Engler, E.M., Lee, V.Y., Nazzal, A.I., Beyers, R.B., Lim, G., Grant, P.M., Parkin, S.S.P., Ramirez, M.L., Vazquez, J.E., Savoy, R.J.: J. Am. Chem. Soc. (1987)
4. Fisk, Z., Thompson, J.D., Zirngiebl, E., Smith, J.L., Cheong, S.W.: Solid State Commun.62, 743 (1987)
5. Ku, H.C., Yang, H.D., McCallum, R.W., Noack, M.A., Klavins, P., Shelton, R.N., Moodenbaugh, A.R.: Extended abstracts, high temperature superconductors. Gubsen, D.U., Schluter, M. (eds.): Mater. Res. Soc. (Pittsburgh 1987); p. 177