1. See for example papers in Novel Superconductivity, ed. S.A. Wolf and V.Z. Kresin (Plenum New York, 1987).
2. Y. Ueda and K. Kosuge, Physica, C156 (1988) 281.
3. J.M. Tranquada, A.H. Moudden, A.I. Goldman, P. Zolliker, D.E. Cox, G. Shirane, S.K. Sinha, D. Vaknin, D.C. Johnston, M.S. Alvarez and A.J. Jacobson, Phys. Rev. B.
4. N. Nishida et al., J. Phys. Soc. Jpn., 57 (1988) 597
5. J.H. Brewer et al., Phys. Rev. Lett., 60 (1988) 1073.