1. “:Ba2.1Bi0.9(O, F)6.8-: a new ordered anion-excess fluorite”. Prituzhalov VA, Abakumov AM, Ardashnikova EI, Dolgikh VA, Van Tendeloo G, Materials research bulletin 42, 861 (2007).   http://doi.org/10.1016/j.materresbull.2006.08.023