A sketch of the fundamentals of Lobachevskian geometry. Prepared for publication by I.N. Bronshtein. Translated from the 1st Russian ed. by Leo F. Boron, with the assistance of Ward D. Bouwsma
A translation of the author's [Kratkiĭ ocherk osnov geometrii Lobachevskogo] reprinted with changes, in 1950 in [Stroenie neevklidovoĭ geometrii], by P.A. Shirokov and V.F. Kagan