Yttrium

ChemGlobe: Yttrium - Electronic, thermal, and steric data along with an isotope table.
partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/39.html

ChemicalElements.com: Yttrium - Basic information, atomic structure, and isotopes.
www.chemicalelements.com/elements/y.html

The Columbia Encyclopedia: Yttrium - Overview for the general reader.
www.bartleby.com/65/yt/yttrium.html

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

It's Elemental: Yttrium - Basic physical and historical information.
education.jlab.org/itselemental/ele039.html

LANL: Yttrium - History, sources, properties, uses, and isotopes.
periodic.lanl.gov/elements/39.html

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

Visual Elements: Yttrium - Image, animation, uses, physical information, and ionisation energies.
www.chemsoc.org/viselements/pages/yttrium.html

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