1. Gallagher, P. K., O'Bryan, H. M., Sunshine, S. A. & Murphy, D. W. Mater. Res. Bull. 22, 995–1006 (1987).
2. Chaillout, C. & Remeika, J. P. Solid St. Commun. 56, 833–836 (1985).
3. Cava, R. J. et al. Phys. Rev. Lett. 58, 1676–1679 (1987).
4. Muller, J. Pap. presented at Eur. Workshop High T c Superconductors and Potential Applications, Genoa, 1–3 July (1987).
5. Johnston, D. C., Jacobson, A. J., Newsana, J. M., Lewandowski, J. T. & Goshorn, D. P. Pap. presented at Am. chem. Soc. Meet. New Orleans (31 August–4 September, 1987).