11Miss Brooks, Phil. Mag. Sept. 1904.12Rutherford y Soddy, Trans. Chem. Soc. 81, p. 837, 1902. Phil. Mag. nov. 1902.13Miss Brooks, Phil. Mag. Sept. 1904.14Rutherford, Phil. Trans. A. p. 169, 1904.15Giesel, Ber. d. D. Chem. Ges. p. 775, 1905.16Godlewski, Nature, p. 294, 19 de ene. de 1905.17Debierne, C. R. 138, p. 411, 1904.18Miss Brooks, Phil. Mag. Sept. 1904.