Byron, FW., Joachain, CJ., & Potvliege, RM. (1982). Unitarization of the Eikonal-born Series Method for Electron-atom and Positron-atom Collisions. Journal of Physics B: Atomic, Molecular and Optical Physics, 15(21), 3915-3943. https://doi.org/10.1088/0022-3700/15/21/014 (Original work published 1982)