1. M. Abramowitz, I.A. Stegun, Handbook of Mathematical Functions, Dover, New York, 1989.
2. Boundary layer problems exhibiting resonance;Ackerberg;Studies Appl. Math.,1970
3. C.M. Bender, S.A. Orszag, Advanced Mathematical Methods for Scientists and Engineers, McGraw-Hill, New York, 1978.
4. F.W.J. Olver, Asymptotics and Special Functions, Academic Press, New York, 1974.
5. F.W.J. Olver, Second-order linear differential equations with two turning points, Philos. Trans. Roy. Soc., London Ser. A 278 (1975) 137–174.