Spectral shifts in general relativity, Jayant V. Narlikar, Am. J. Phys. 62(1), October 1994
A unified approach towards spectral shifts in general relativity brings the cosmological redshift within the same framework as he more familiar Doppler effect. This approach was first proposed by Synge [Relativity: The General Theory (North Holland, Amsterdam (1960)] and is described here in a more simplified form