Mary Elvira Weeks(1932)."The discovery of the elements. XII. Other elements isolated with the aid of potassium and sodium: Beryllium, boron, silicon, and aluminum".Journal of Chemical Education9(8): 1386.doi:10.1021/ed009p1386.Bibcode:1932JChEd...9.1386W.
Mary Elvira Weeks(1933)."The discovery of the elements. XIX. The radioactive elements".Journal of Chemical Education10(2): 79.doi:10.1021/ed010p79.Bibcode:1933JChEd..10...79W.
Mary Elvira Weeks(1932)."The discovery of the elements. XII. Other elements isolated with the aid of potassium and sodium: Beryllium, boron, silicon, and aluminum".Journal of Chemical Education9(8): 1386.doi:10.1021/ed009p1386.Bibcode:1932JChEd...9.1386W.
Mary Elvira Weeks(1933)."The discovery of the elements. XIX. The radioactive elements".Journal of Chemical Education10(2): 79.doi:10.1021/ed010p79.Bibcode:1933JChEd..10...79W.
Richard B. Firestone (15 March 2010). "Isotopes of Calcium (Z=20)". Lawrence Berkeley National Laboratory. Archived from the original on 6 May 2012. Retrieved 12 June 2012.
Richard B. Firestone (15 March 2010). "Isotopes of Barium (Z=56)". Lawrence Berkeley National Laboratory. Archived from the original on 6 May 2012. Retrieved 12 June 2012.
Richard B. Firestone (15 March 2010). "Isotopes of Calcium (Z=20)". Lawrence Berkeley National Laboratory. Archived from the original on 6 May 2012. Retrieved 12 June 2012.
Richard B. Firestone (15 March 2010). "Isotopes of Barium (Z=56)". Lawrence Berkeley National Laboratory. Archived from the original on 6 May 2012. Retrieved 12 June 2012.