Georges Lemaître, Un univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques, in Annales de la Société Scientifique de Bruxelles, A47, 1927, pp. 49–59, Bibcode:1927ASSB...47...49L.. Partially translated (the translator remains unidentified) in Georges Lemaître, Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulæ, in Monthly Notices of the Royal Astronomical Society, vol. 91, 1931, pp. 483–490, Bibcode:1931MNRAS..91..483L..