German Wikipedia, viewed Nov. 6, 2013 (Felix Klein, Christian Felix Klein; b. Apr. 25, 1849, in Düsseldorf; d. June 22, 1925, in Göttingen; German mathematician; developed influential Erlanger Programm on how to classify and characterize geometries) http://de.wikipedia.org/wiki/Felix_Klein
LCCN 22-22305: His Gesammelte mathematische Abhandlungen, 1921-23 (hdg.: Klein, Felix, 1849-1925; variants: ... F. Kleins; Christian Felix Klein)