1. Gmelin 8th ed. Seltene Erden A2 - A5, B1 - B7, C1 - C3, C4 a, C5 - C6, C8, D1 - D3.
2. Handbook on the Physics and Chemistry of Rare Earths
3. L. Eyring Progress in the Science and Technology of the Rare Earths 1, 1964; vol. 2 1966; vol. 3, 1968 Pergamon Press Oxford