Sturm’s 1836 Oscillation Results Evolution of the Theory -- Sturm Oscillation and Comparison Theorems -- Charles Sturm and the Development of Sturm-Liouville Theory in the Years 1900 to 1950 -- Spectral Theory of Sturm-Liouville Operators Approximation by Regular Problems -- Spectral Theory of Sturm-Liouville Operators on Infinite Intervals: A Review of Recent Developments -- Asymptotic Metho…