Alexander A. Friedmann, Papers On Curved Spaces and Cosmology (Minkowski Institute Press, Montreal 2014), 74 pages
http://www.minkowskiinstitute.org/mip/books/friedmann2.html
This book contains three papers by Friedmann – “On the Curvature of Space” (1922), “On the Possibility of a World with a Constant Negative Curvature of Space” (1924), and “On the Geometry of Curved Spaces”. The third paper is a 28-page manuscript (dated 15 April 1922) which has not been published even in Russian.
Unlike the existing two English translations of Friedmann’s 1922 and 1924 papers (done from the German publications), now these papers are translated directly from the original Russian texts.
Vesselin Petkov