Editor's note: ''On the curvature of space'' by A. Friedman and ''On the possibility of a world with constant negative curvature of space'' by A. Friedmann
Introductory remarks to the two papers of \textit{A. Friedmann} (A. A. Fridman) reprinted in this issue. For reviews of the originals [Z. Phys. 10, 377-386 (1922) and ibid. 21, 326-332 (1924) see JFM 48.1031.02 and JFM 50.0577.01]. Russian translations of these papers were published in Usp. Fiz. Nauk 80, No. 3, p. 439 and 447 (1963), along with Russian translations of the two notes by \textit{A. Einstein} [see Z. Phys. 11, 326 (1922; JFM 48.1031.03) and ibid. 16, 228 (1923; JFM 49.0652.01)], Friedmann's biography and essays on Friedmann's work by V. A. Fok, Ya. B. Zel'dovich, E. M. Lifshitz and I. M. Khalatnikov. A Russian translation of the first paper by Friedmann was also published in 1924 in the J. Russ. Phys. Chem. Soc. (Zh. Russ. Fiz. Chim. Obsh.).
metrics of spatially homogeneous and isotropic spacetimes
scientific article; zbMATH DE number 1423710