1. Abrami, A.: 1966,Mem. Soc. Astron. Italiana 37, 369.
2. Braune, W.: 1967,BAV Mitteilungen, No. 18, 107.
3. Geyer, E. (cf. Kukarkin, B. V., Efremov, Yu. I., and Kholopov, P. N.): 1960,First Supplement to the Second Edition of the General Catalogue of Variable Stars (1958), p. 28.
4. Harper, W. E., Pearce, J. A., Petrie, R. M. and McKellar, A.: 1935,J. Roy. Astron. Soc. Canada 29, 411.
5. Isles, J. E.: 1986,J. Brit. Astron. Assoc. 96, No. 5, 294.