Dear Pavel Sigizmundovich, I'm sending you a brief note regarding the question about the possible shape of the universe more general than the cylindrical world of Einstein, and the spherical world of De Sitter; aside from these two cases there appears also a world, the space of which possesses a curvature radius _varying_ with time; it seemed to me that a question of this sort may interest you or De Sitter. In the near future I will send you a German translation of this note, if you find the question considered in it interesting, then please be so kind to have it placed in some journal. Send my regards to Tatyana Alekseevna. Please be so kind, due to mail malfunction, to confirm the receipt of this letter. 3 June 1922, Sincerely yours, A. Friedmann P.S. Please be so kind to ask De Sitter to send me an offprint of his work "On Einsteins theory etc"; Monthly Notices R. Acad. Soc. 1917. It can be found in Pulkovo, but getting the journal from there is almost impossible, and walking over there is very hard. Petrograd, Main Physics Observatory, to Friedmann.