“The electronic structure of ZnO and ZnF determined by anion photoelectron spectroscopy”, Vicki D. Moravec, Stephan A. Klopcic, Bappaditya Chatterjee, and Caroline Chick Jarrold,Chemical Physics Letters, 341, 313 (2001). https://doi.org/10.1016/S0009-2614(01)00465-1