1. E.R. Scerri, J. Sci. Educ. 12, 4 (2011).
2. A. Hérold, C. R. Chim. 9, 148 (2006).
3. M-L. Kamberg, The Transition Elements: The 37 Transition Metals, 1st ed. (New York: The Rosen Publishing Group Inc., 2010).
4. M. Halka and B. Nordstrom, Periodic Table of the Elements—Transition Metals (New York: Facts On File Inc, 2011).
5. H. Merz and K. Ulmer, Phys. Lett. 26, 1 (1967).