Gadolinium

Lenntech: Gadolinium - Physical data, chemical properties, health and environmental effects.
http://www.lenntech.com/Periodic-chart-elements/Gd-en.htm

Corrosionsource.com: Gadolinium - History, occurrence, properties, isotopes, and uses.
http://www.corrosionsource.com/handbook/periodic/64.htm

WebElements: Gadolinium - Extensive information on history, uses, occurrence, compounds, and properties.
http://www.webelements.com/gadolinium/

EnvironmentalChemistry.com: Gadolinium - Atomic structure, chemical and physical properties, and table of nuclides.
http://environmentalchemistry.com/yogi/periodic/Gd.html

ChemicalElements.com: Gadolinium - Basic information, atomic structure, and isotopes.
http://www.chemicalelements.com/elements/gd.html

Visual Elements: Gadolinium - Image, source, uses, physical information, and key isotopes.
http://www.chemsoc.org/viselements/pages/gadolinium.html

ChemGlobe: Gadolinium - Electronic, thermal, and steric data along with an isotope table.
http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/64.html

LANL: Gadolinium - History, sources, properties, and uses.
http://periodic.lanl.gov/elements/64.html

It's Elemental: Gadolinium - Basic physical and historical information.
http://education.jlab.org/itselemental/ele064.html

Wikipedia: Gadolinium - Properties of the element, including its history, applications, and characteristics.
http://en.wikipedia.org/wiki/Gadolinium