Hawley chem. dict. (lanthanide series (lanthanoid series): the rare earth series of elements, atomic nos. 58-71)

McGraw-Hill dict. sci. tech. (rare earth element: the name given to any of the group of chemical elements with the atomic numbers 58 to 71)

Random House (rare earth element. Also called rare earth metal)

Engr. index (Rare earth elements)

ASTI (Rare earth metals)

INSPEC (Rare earth metals UF Rare earth elements)