See also:

• Science: Chemistry: Elements: Actinides  (1)

• ChemGlobe: Protactinium - Electronic, thermal, and steric data along with an isotope table.
• ChemicalElements.com: Protactinium - Basic information, atomic structure, and isotopes.
• EnvironmentalChemistry.com: Protactinium - Atomic structure, chemical and physical properties, and table of nuclides.
• It's Elemental: Protactinium - Basic physical and historical information.
• LANL: Protactinium - Basic information and history.
• Visual Elements: Protactinium - General and physical information, source, and key isotopes.
• WebElements: Protactinium - Extensive information on history, uses, occurrence, compounds, and properties.

• Radiochemistry of Protactinium - Full text of the monograph by H. W. Kirby (Mound Laboratory, Miamisburg, Ohio). [PDF] (December, 1959)