Explanation:
"dictionary.reference"  Nov. 8, 2003 http://dictionary.reference.com/search?q=niobium

"rembar" Nov. 10, 2003  http://www.rembar.com/niobium.htm

Properties:
"chemical elements" Nov. 5, 2003  http://www.chemicalelements.com/elements/nb.html

"wild-turkey" Nov. 5, 2003  http://wild-turkey.mit.edu/Chemicool/elements/niobium.html

Isotopes:
"enviromentalchemistry" Nov. 5, 2003  http://environmentalchemistry.com/yogi/periodic/Nb.html