1. G. H. Herbig, Astrophys. J. 131, 632 (1960).
2. V. I. Kardapolov, V. V. Sakhanenok, and N. A. Shutemova, Peremennye zvezdy 21, 283 (1980).
3. A. F. Pugach, Astrophysics 17, 47 1981).
4. G. V. Zaitseva, Peremennye zvezdy 22, 181 (1985).
5. W. Wenzel, IAU Inform. Bull. Var. Stars 3280, 1 (1989).