1. See, for example, Birgeneau, R.J., Shirane, G.: In: Physical properties of high temperature superconductors I. Ginsberg, D.M. (ed.), pp. 151?212. Singapore: World Scientific 1989; Birgeneau, R.J.: Am. J. Phys.58, 28 (1990)
2. Shirane, G.: In: Proceedings of the M2S-HTSC III International Conference, July 22?26, 1991, Kanazawa, Japan; Tranquada, J.: Proceedings of the University of Miami Workshop on Electronic Structure and Mechanisms for High Temperature Superconductivity, January 1991, Ashkenazi, J., Vezzoli, G. (eds.). New York: Plenum 1991
3. Rossat-Mignod, J., Regnault, L.P., Vettier, C., Burlet, P., Henry, J.Y., Lapentot, G.: Physica B169 58 (1991) and (unpublished)
4. Keimer, B., Birgeneau, R.J., Cassanho, A., Endoh, Y., Erwin, R.W., Kastner, M.A., Shirane, G.: Phys. Rev. Lett.67, 1930 (1991) and (unpublished)
5. Tranquada, J.M., Shirane, G., Keimer, B., Shamoto, S., Sato, M.: Phys. Rev. B40, 4503 (1989)