Landrum, G. A., Dronskowski, R., Niewa, R., & DiSalvo, F. J. (1999). Electronic Structure and Bonding in Cerium (Nitride) Compounds: Trivalent versus Tetravalent Cerium. Chemistry - A European Journal, 5, 515-522. doi:10.1002/(SICI)1521-3765(19990201)5:2<515:AID-CHEM515>3.0.CO;2-Y.