Abstract
The authors investigate the correspondence between the singularities of Sturm-Liouville expansions of the form ?n vn(z), Where the vn(z) are the normalized eigenfunction expansions of a regular second order Sturm-Liouville eigenvalue problem, with the singularities of the power series an a n. It is shown if is a singularity of power series on its radius of convergence then the Sturm-Liouville series is singular at both the points z1=arg?-iin|?|,and z2=-z1