Coşkun, Haskiz, and Ayşe Kabataş. 2013. “Asymptotic Approximations of Eigen-Functions for Regular Sturm-Liouville Problems With Eigenvalue Parameter in the Boundary Condition for Integrable Potential”. MATHEMATICA SCANDINAVICA 113 (1):143-60. https://doi.org/10.7146/math.scand.a-15486.