Linear algebra
He lived in Belgrade until his death in 1947, active as a university professor up until Yugoslavia was invaded by Nazi Germany in 1941. Before the turn of the century he had published two voluminous university textbooks—900-page "Analytical Geometry" (1896), and "Theory of Determinants" (1899) on Linear algebra. Both works may be considered as capital works in mathematics in Serbia. Academician Radivoj Kašanin once wrote: