1. For obvious reasons we cannot quote all the papers pertaining to substitution in YBCO 123. We will only quote, hopefully all, papers reporting on the substitution of Na, K, and Cs elements which we only consider herein. We apologize for overlooking any other paper of interest. One should note that we do not consider the case of Li nor Rb-doping
2. Ausloos, M., Laurent, Ch., Vanderschueren, H.W., Rulmont, A., Tarte, P.: Solid State Commun.68, 539 (1988)
3. Ausloos, M., Laurent, Ch., Vanderschueren, H.W., Rulmont, A., Tarte, P.: Physica C153?155, 1351 (1988)
4. Ausloos, M., Laurent, Ch., Vanderschueren, H.W., Rulmont, A., Tarte, P.: Phys. Rev. B39 (1989)
5. Saito, Y., Noji, T., Endo, A., Higuchi, N., Fujimoto, K., Oikawa, T., Hattori, A., Furuse, K.: Physica B148, 336 (1987)