See also:

• Science: Chemistry: Elements: Lanthanides  (2)

ChemGlobe: Promethium - Electronic, thermal, and steric data along with an isotope table..

ChemicalElements.com: Promethium - Basic information, atomic structure, and isotopes..

EnvironmentalChemistry.com: Promethium - Atomic structure, chemical and physical properties, and table of nuclides..

It's Elemental: Promethium - Basic physical and historical information..

LANL: Promethium - History, sources, uses, and properties..

Lenntech: Promethium - Physical data, chemical properties, health and environmental effects..

Visual Elements: Promethium - Image, animation, source, uses, and ionisation energies..

WebElements: Promethium - Extensive information on history, uses, occurrence, compounds, and properties..

Wikipedia: Promethium - Properties of the element, including its history, applications, and characteristics..