One of the greatest German mathematicians of his era, Felix Klein (1849-1925) taught at the University of Göttingen from 1887 until his retirement in 1913. He made major contributions to many areas of mathematics, including group theory, complex analysis, and non-Euclidean geometry. Dover also publishes Klein's classic two-volume work, Elementary Mathematics from an Advanced Standpoint, part one of which focuses on geometry and part two on arithmetic, algebra, and analysis.