1. Andriesse, C. D.: 1985, inPhysical Processes in Red Giants, D. Reidel Publ. Co., Dordrecht, Holland, p. 351.
2. Baron, Y., de Muizon, M., Papoular, R., and Pegourie, B.: 1987,Astron. Astrophys. 186, 271.
3. Bergeat, J. and Sibai, A. M.: 1983,Astron. Astrophys. 119, 207.
4. Bergeat, J., Sibille, F., Lunel, M., and Lefevre, J.: 1976,Astron. Astrophys. 52, 227.
5. Boothroyd, A. I. and Sackmann, I. J.: 1988,Astrophys. J. 328, 632.