hafnium
1982 / Some Details in the Prehistory of the Discovery of Element 72 / V. P. Mel'nikov / Centaurus 26 (1982) p. 317 [doi]
1994 / Prediction of the nature of hafnium from chemistry, Bohr's theory and quantum theory / Eric R. Scerri / Annals of Science 51 (1994) p. 137 [doi]