ChemGlobe: Polonium - Electronic, thermal, and steric data along with an isotope table. - http://partisans.spurious.biz/~pkremer/projects/chemglobe/ptoe/_/84.html
LANL: Polonium - Sources, properties, uses, and isotopes. - http://periodic.lanl.gov/elements/84.html
Wikipedia: Polonium - Properties of the element, including its history, applications, and characteristics. - http://en.wikipedia.org/wiki/Polonium
Lenntech: Polonium - Physical data, chemical properties, health and environmental effects. - http://www.lenntech.com/Periodic-chart-elements/Po-en.htm
EnvironmentalChemistry.com: Polonium - Atomic structure, chemical and physical properties, and table of nuclides. - http://environmentalchemistry.com/yogi/periodic/Po.html
Visual Elements: Polonium - Image, general and physical information, source, uses, key isotopes, and ionisation energies. - http://www.chemsoc.org/viselements/pages/polonium.html
ChemicalElements.com: Polonium - Basic information, atomic structure, and table of isotopes. - http://www.chemicalelements.com/elements/po.html
Radiochemistry of Polonium - Full text of the monograph by P. E. Figgins (Mound Laboratory, Miamisburg, Ohio). [PDF] - http://lib-www.lanl.gov/cgi-bin/getfile?rc000006.pdf