Über die Möglichkeit einer Welt mit konstanter negativer Krümmung des Raumes [with] Bemerkung zu der Arbeit von A. Friedmann Über die Krümmung des Raumes; in Zeitschrift für Physik

Berlin: Springer, 1922. First Edition. Wrappers. Near fine. 2 vols. 1st editions (in German), the first appearance of 2 distinct papers, in 2 separate periodical issues, September 13 and November 17. Both are complete in original wrappers. Near fine (small pencil name on the Nov. cover). Seems to be surprisingly rare. RBH lists no auction sales of Friedmann's article title and date since 1975, and only one copy of it is listed by OCLC, but copies of the bound annual, Zeitschrift für Physik, are regularly available and should not, in this case, be considered, in any way, equivalent to our set in publisher's wrappers. 1. Friedmann's pioneering paper, the first to seriously apply general relativity to cosmology without the stabilizing cosmological constant, theorizing and mathematically formularizing, an expanding universe, dragging cosmology into a branch of physics. In Zeitschrift für Physik, Band 10, He 16, September 13, 1922, pages 377-386,

"Here we have, for the first time, the idea of an expanding universe originating in a singularity-a big-bang." -Helge Kragh, Cosmology and Controversy, page 24.

2. Einstein's critical remarks on Friedmann's paper that he retracted in 1923. In Zeitschrift für Physik, Band 11, He 4/5, November 17, 1922, page 326.