Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes, vol. 21, Bibcode:1924ZPhy...21..326F, DOI:10.1007/BF01328280. English trans. in 'General Relativity and Gravitation' 1999 vol.31, 31–
Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulae, vol. 91, Bibcode:1931MNRAS..91..483L, DOI:10.1093/mnras/91.5.483. tradotto daUn Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques, A47, Bibcode:1927ASSB...47...49L.
Vedere pp. 351 e seguenti in The Large Scale Structure of Space-Time, ISBN978-0-521-09906-6.. Il lavoro originale è Ehlers, J., Geren, P., Sachs, R.K.: Isotropic solutions of Einstein-Liouville equations. J. Math. Phys. 9, 1344 (1968). Per la generalizzazione, vedere Proving Almost-Homogeneity of the Universe: an Almost Ehlers-Geren-Sachs Theorem, vol. 39, Bibcode:1995ApJ...443....1S, DOI:10.1086/175496..
Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes, vol. 21, Bibcode:1924ZPhy...21..326F, DOI:10.1007/BF01328280. English trans. in 'General Relativity and Gravitation' 1999 vol.31, 31–
Expansion of the universe, A homogeneous universe of constant mass and increasing radius accounting for the radial velocity of extra-galactic nebulae, vol. 91, Bibcode:1931MNRAS..91..483L, DOI:10.1093/mnras/91.5.483. tradotto daUn Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques, A47, Bibcode:1927ASSB...47...49L.
Vedere pp. 351 e seguenti in The Large Scale Structure of Space-Time, ISBN978-0-521-09906-6.. Il lavoro originale è Ehlers, J., Geren, P., Sachs, R.K.: Isotropic solutions of Einstein-Liouville equations. J. Math. Phys. 9, 1344 (1968). Per la generalizzazione, vedere Proving Almost-Homogeneity of the Universe: an Almost Ehlers-Geren-Sachs Theorem, vol. 39, Bibcode:1995ApJ...443....1S, DOI:10.1086/175496..