Table: A Historical Analysis. Gschneider, Karl A., Jr.; Bünzli, Jean-Claude; Pecharsky, Vitalij K. (编). Handbook on the Physics and Chemistry of Rare Earths
Hedrick, James B. Rare-Earth Metals (PDF). USGS. [2009-06-06]. (原始内容存档 (PDF)于2011-01-10). Castor, Stephen B.; Hedrick, James B. Rare Earth Elements (PDF). [2009-06-06]