Used with
permission of Maiken Naylor, University at Buffalo, Buffalo, NY, USA,
http://ublib.buffalo.edu/libraries/units/sel/exhibits/stamps
Nikolai Lobachevsky (1792-1856) was a Russian mathematician who published the first non-Euclidean geometry, which does not make use of Euclid's fifth postulate, but treats Euclidian geometry as a special case.