Coskun, Haskiz, and Elif Baskaya. 2010. “Asymptotics of Eigenvalues of Regular Sturm-Liouville Problems With Eigenvalue Parameter in the Boundary Condition for Integrable Potential”. MATHEMATICA SCANDINAVICA 107 (2):209-23. https://doi.org/10.7146/math.scand.a-15152.