Fröman, N., & Fröman, P. O. (2008). Stark effect in a hydrogenic atom or ion: Treated by the phase-integral method. Imperial College Press ; Distributed by World Scientific Publishing.

Fröman, Nanny, and Per Olof Fröman. Stark Effect in a Hydrogenic Atom or Ion: Treated by the Phase-integral Method. London : Hackensack, NJ: Imperial College Press ; Distributed by World Scientific Publishing, 2008.

Fröman, Nanny, and Per Olof Fröman. Stark Effect in a Hydrogenic Atom or Ion: Treated by the Phase-integral Method. Imperial College Press ; Distributed by World Scientific Publishing, 2008.