Schmidt, E. W., Schippers, S., Bernhardt, D., Müller, A., Hoffmann, J., Lestinsky, M., et al. (2008). Electron-ion recombination for Fe viii forming Fe vii and Fe ix forming Fe viii: Measurements and theory. Astronomy and Astrophysics, 492, 265-275. doi:10.1051/0004-6361:200810834.