1. Berghöfer, T.W., Schmitt, J.H.M.M.: 1993a, Proc. IAU-Symp. 162 on Pulsation, Rotation and Mass Loss in Early-Type Stars, eds. L. Balona et al., Kluwer Publishers
2. Berghöfer, T.W., Schmitt, J.H.M.M.: 1993b, in preparation forAstron. Astrophys.
3. Cassinelli, J.P., Olson, G.L., 1979,Astrophys. J. 229, 304
4. Chlebowski, T., Harnden, F.R., Jr., Sciortino, S.: 1989,Astrophys. J. 341, 427
5. Collura, A., et al.: 1989,Astrophys. J. 338, 296