Helmholtz Differential Equation--Oblate Spheroidal Coordinates

As shown by Morse and Feshbach (1953) and Arfken (1970), the Helmholtz Differential Equation is separable in Oblate Spheroidal Coordinates.

References

Arfken, G. ``Oblate Spheroidal Coordinates $(u, v, \varphi)$.'' §2.11 in Mathematical Methods for Physicists, 2nd ed. Orlando, FL: Academic Press, pp. 107-109, 1970.

Morse, P. M. and Feshbach, H. Methods of Theoretical Physics, Part I. New York: McGraw-Hill, p. 662, 1953.