Weeks, Mary Elvira (1932). "The discovery of the elements. XI. Some elements isolated with the aid of potassium and sodium: Zirconium, titanium, cerium, and thorium". Journal of Chemical Education. 9 (7): 1231. Bibcode:1932JChEd...9.1231W. doi:10.1021/ed009p1231.
Weeks, Mary Elvira (1932). "The discovery of the elements. XI. Some elements isolated with the aid of potassium and sodium: Zirconium, titanium, cerium, and thorium". Journal of Chemical Education. 9 (7): 1231. Bibcode:1932JChEd...9.1231W. doi:10.1021/ed009p1231.