Prepd from CeF3 and F2: Klemm, Henkel, Z. Anorg. Allg. Chem. 220, 181 (1934); von Wartenberg, ibid. 244, 343 (1940); Kwasnik in Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 247-248; from CeO2 and F2: Asker, Wylie, Aust. J. Chem. 18, 959 (1965).