Asymptotic Expansions of Mathieu Functions and their Characteristic Numbers. R.B. Dingle; H.J.W. Müller — 1962 Journal für die reine und angewandte Mathematik
The Form of the Coefficients of the Late Terms in Asymptotic Expansions of the Characteristic Numbers of Mathieu and Spheroidal-Wave Functions. R.B. Dingle; H.J.W. Müller — 1964 Journal für die reine und angewandte Mathematik