1. 1.A. V. Zasov and K. A. Postnov, Basic Astrophysics (Mosk. Gos. Univ., Moscow, 2006) [in Russian].
2. 2. Stellar atmospheres, Ed. by J. L. Greenstein (Univ. of Chicago Press, Chicago, 1960; Inostrannaya Literatura, Moscow, 1963).
3. 3.K. A. Postnov and A. V. Zasov, A Course of Basic Astrophysics (Mosk. Gos. Univ., Moscow, 2005) [in Russian].
4. 4.V. V. Sobolev, A Course of Theoretical Astrophysics (Nauka, Moscow, 1967) [in Russian].
5. 5.P. Antolin and R. L. van der Voort., "Observing the fine structure of loops through high-resolution spectroscopic observations of Coronal rain with the Crisp instrument at the Swedish telescope," Astrophys. J. 745, 152-173 (2012).