References
Heiserman, David L. Exploring Chemical Elements and their Compounds, Ytterbium. New York: Tab Books, McGraw-Hill. 1992. pp 248-250
Winter, Mark. Web Elements. http://www.shef.ac.uk/~chem/web-elements/main/index-nofr.html. 1998. January 20, 1998.
Periodic Table of the Elements. http://mwanal.lanl.gov/CST/imagemap/periodic/periodic.html. 1997. January 22, 1998.