Lenntech: Thulium Lenntech: Thulium: Physical data, chemical properties, health and environmental effects. (Thulium) http://www.lenntech.com/Periodic-chart-elements/Tm-en.htm
WebElements: Thulium WebElements: Thulium: Extensive information on history, uses, occurrence, compounds, and properties. (Thulium) http://www.webelements.com/webelements/elements/text/Tm/key.html
EnvironmentalChemistry.com: Thulium EnvironmentalChemistry.com: Thulium: Atomic structure, chemical and physical properties, and table of nuclides. (Thulium) http://environmentalchemistry.com/yogi/periodic/Tm.html
ChemGlobe: Thulium ChemGlobe: Thulium: Electronic, thermal, and steric data along with an isotope table. (Thulium) http://www.vcs.ethz.ch/chemglobe/ptoe/_/69.html