1. P. N. Kholopov et al.,General Catalogue of Variable Stars, Fourth Ed., Moscow, Nauka, 1985.
2. K. A. Grigoryan,Soob. Byurakan Obs.,25, 45, 1958.
3. N. M. Shakhovskoj,Astron. Zh.,40, 1055, 1963.
4. K. Serkowski,Astrophys. J.,144, 857, 1966.
5. R. A. Vardanian,Astrofizika,4, 152, 1968.