Geometrische Untersuchungen zur Theorie der Parallellinien
Mayer & Müller, Berlin, 1887
115. Lobachevskii developed a new system of geometry that was not dependent on Euclid's parallel postulate. His system of non-Euclidean geometry was first published in an obscure journal in Kazan, Russia. His work was noticed by Gauss, who also developed a similar system independently, and Lobachevskii was finally recognized for his achievements in the 1840s.