1. Bertelli, G., Bressan, A., Chiosi, C., Fagotto, F., Nasi, E. (1994). A&AS, 106, 275.
2. Castelli, F., (1991). A&A, 251, 106.
3. Dworetsky, M.M and Moon, T.T. (1986). MNRAS, 220, 787.
4. Guthrie, B.N.G. (1987). MNRAS, 226, 361.
5. Hauck, B. and North P. (1993). A&A, 269, 403.