1. J. M. Tranquada, D. E. Cox, W. Kunnman et al., Phys. Rev. Lett. 60, 156 (1988).
2. P. Burlet, J. Y. Henry, and L. P. Regnault, Physica C 296, 205 (1998).
3. V. G. Bar’yakhtar, V. M. Loktev, and D. A. Yablonskii, Sverkhprovodimost’ (KIAE) 2, 32 (1989) [Superconductivity 2, 28 (1989)].
4. L. A. Boyarskii and V. Ya. Dikovskii, Fiz. Nizk. Temp. 2, 1297 (1976) [Sov. J. Low Temp. Phys. 2, 632 (1976)].
5. Y. Ando, A. N. Lavrov, and K. Segawa, http://xxx.lanl.gov/abs/cond-mat/9905071 .