Sidis, V., Kubach, C., & Fussen, D. (1983). Ionic-covalent Problem in the H++h(-)-reversible-h-star+h Collisional System. Physical review. A, Atomic, molecular, and optical physics, 27(5), 2431-2446. https://doi.org/10.1103/PhysRevA.27.2431 (Original work published 1983)