ChemGlobe: Terbium - Electronic, thermal, and steric data along with an isotope table. - http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/65.html
LANL: Terbium - History, production, properties, and uses. - http://periodic.lanl.gov/elements/65.html
Wikipedia: Terbium - Properties of the element, including its history, applications, and characteristics. - http://en.wikipedia.org/wiki/Terbium
Lenntech: Terbium - Physical data, chemical properties, health and environmental effects. - http://www.lenntech.com/Periodic-chart-elements/Tb-en.htm
EnvironmentalChemistry.com: Terbium - Atomic structure, chemical and physical properties, and table of nuclides. - http://environmentalchemistry.com/yogi/periodic/Tb.html