Byron, FW., Joachain, CJ., & Piraux, B. (1983). Triple Differential Cross-sections for the Ionization of Atomic-hydrogen By Fast Electrons. Physics Letters. Section A: General, Atomic and Solid State Physics, 99(9), 427-431. https://doi.org/10.1016/0375-9601(83)90949-0 (Original work published 1983)