1. Sturm–Liouville Theory: Past and Present;Amrein,2005
2. Sturm–Liouville Theory, vol. 121;Zettl,2010
3. An Introduction to the Fractional Calculus and Fractional Differential Equations;Miller,1993
4. Fractional Differential Equations;Podlubny,1999
5. Theory and Applications of Fractional Differential Equations;Kilbass,2006