1. Athay, R. G.: 1970, Solar Phys. 12, 175.
2. Beckers, J. M. and Milkey, R. W.: 1975, Solar Phys. 43, 289.
3. Beckers, J. M. and Canfield, R. C.: 1975, in R. Cayrel and M. Steinberg (eds.), ?Physique des mouvements dans les atmosph�res Stellaires?, CNRS Colloq. 250, 207.
4. Brault, J. and Testerman, L.: 1972, Kitt Peak Solar Atlas, Prelim. Ed.
5. Canfield, R. C.: 1975, Unpublished.