Mikailov Khidir Mustafa, Mammadov Ruslan Tavakkul, Rustamov Bayram Nizam, and Rustamova Aysel Bayram. “Spectral Variability of the Symbiotic Star CH Cyg”. Proceedings of the Pakistan Academy of Sciences: A. Physical and Computational Sciences, vol. 60, no. 1, Mar. 2023, pp. 9-13, doi:10.53560/PPASA(60-1)671.