Lemaître, Georges (1927). «Un univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques». Annales de la Société Scientifique de Bruxelles. A47: 49–56. Bibcode:1927ASSB...47...49L. (Full article, PDF). Partially translated (the translator remains unidentified) in Lemaître, Georges (1931). «Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulæ». Monthly Notices of the Royal Astronomical Society. 91: 483–490. Bibcode:1931MNRAS..91..483L.