Moving Envelopes of Stars, by V.V. Sobolev, translated by Sergei Gaposchkin, hardcover (very good condition)
 
This book presents a theory of radiative equilibrium of a moving medium, applying it to the moving envelopes of stars.
 
The theory of radiative transfer in a moving medium is applied to separate cases in an order of increasing complication. The author shows how a definite class of observed objects corresponds to each case (stars of early spectral classes with bright lines, planetary nebulae, envelopes of new stars, stars of later classes with bright lines).
 
The author calculates the contours and the intensities of bright lines formed by the moving envelopes and determines the physical conditions in the envelopes (ionization of atoms, temperatures, pressure of radiation). The study of such phenomena allows us to penetrate more deeply into the nature of the stars.