1. Bahcall, J.N. and Ulrich, R.K.: 1988, Rev. Mod. Phys. 60, 297.
2. Christensen-Dalsgaard, J.: 1981, Monthly Notices Roy. Astron. Soc. 194, 229.
3. Christensen-Dalsgaard, J.: 1986, in D. O. Gough (ed.), Seismology of the Sun and the Distant Stars, D. Reidel Publ. Co., Dordrecht, Holland.
4. Christensen-Dalsgaard, J.: 1988, in E. J. Rolfe (ed.), Seismology of the Sun and Sun-like Stars, ESA SP-286, p.431.
5. Christensen-Dalsgaard, J., D�ppen, W., and Lebreton, Y.: 1989, Nature 336, 634.