C. Nwoke, LANGER METHOD FOR A 2ND-ORDER LINEAR NONHOMOGENEOUS ORDINARY DIFFERENTIAL-EQUATION WITH SEVERAL DOUBLE POLES, Discovery and innovation, 5(1), 1993, pp. 15-21
Langer's comparison equation method is employed to obtain a uniform as
ymptotic solution for a nonhomogeneous linear ordinary differential eq
uation with several double poles. Asymptotic validity is proved. The r
esults are applied to the acoustic wave scattering by an ellipsoid.