1. Associated Press Report. 1931a. Prof. Einstein begins his work at Mt. Wilson. NYT, Jan 3, p. 1
2. Associated Press Report. 1931b. Redshift of nebulae a puzzle, says Einstein. NYT, Feb 12, p. 2
3. Bartusiak, M. 2009. The Day We Found the Universe. Vintage Books, New York
4. Belenkiy, A. 2012. Physics Today 65 (10): 38-43
5. Belenkiy, A. 2013. The waters I am entering no one yet has crossed: Alexander Friedmann and the origins of modern cosmology. Origins of the Expanding Universe 1912–1932, edited by M. Way and D. Hunter, Astron. Soc. Pacific. Conference Series 471: 71-96