ChemGlobe: Erbium
- Electronic, thermal, and steric data along with an isotope table.
- http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/68.html
LANL: Erbium
- Basic information and history.
- http://periodic.lanl.gov/elements/68.html
Wikipedia: Erbium
- Properties of the element, including its history, applications, and characteristics.
- http://en.wikipedia.org/wiki/Erbium
Lenntech: Erbium
- Physical data, chemical properties, health and environmental effects.
- http://www.lenntech.com/Periodic-chart-elements/Er-en.htm
EnvironmentalChemistry.com: Erbium
- Atomic structure, chemical and physical properties, and table of nuclides.
- http://environmentalchemistry.com/yogi/periodic/Er.html