1. Annuk, K.: 1991, ‘Wolf-Rayet Stars and Interrelations with Other Massive Stars in Galaxies, Proc. IAU Symp.143’ in K.A.van der Hucht and B. Hidayat, ed(s)., Kluwer:Dordrecht, 245
2. Arnal, E.M.: 1992, A& A,254, 305
3. Arnal, E.M., & Mirabel, I.F.: 1991, A& A, 250, 171
4. Aslanov, A.A., & Cherepashchuk, A.M.: 1990, Soviet Astronomy, 34(6), 602
5. Barker, P.K.: 1987, ‘Physics of Be Stars, Proc. 92nd IAU Coll.’ in A. Slettebak and T.P. Snow, ed(s)., Cambridge Univ. Press:Cambridge, 38