Gregory, DC., Meyer, FW., Muller, A., & Defrance, P. (1986). Experimental Cross-sections for Electron-impact Ionization of Iron Ions - Fe5+, Fe6+, and Fe9+. Physical review. A, Atomic, molecular, and optical physics, 34(5), 3657-3667. https://doi.org/10.1103/PhysRevA.34.3657 (Original work published 1986)