1. Appenzeller, I, Wolf, B., Stahl, 0.: 1987, in Instabilities in Luminous Early-type
stars, eds. C. de Loore, A.J. Willis, Reidel, Dordrecht, pg. 241
2. Baars, J.W.M., Wendker, .J.: 1987, Astron. Astrophys.
181, 210
3. Davidson, K., Walborn, N.R., Gull, T.R.: 1982, Astrophys. J. Lett.
254, L47
4. Dufour, R.J., Mitra, P.: 1987, Bull. A.A.S
19, 1090
5. Dufour, R.J., Parker, R.A.R., Henize, K.G.: 1988, Astrophys. J.
327, 859