Has the earth's crust changed with time? : rare earth abundances in ancient sediments /

"May 1967."

The metallurgy of yttrium and the rare earth metals.

"Materials Central, Contract No. AF33(616)-5905, Project No. 7351."

A. Geology and mineral paragenesis of the Pea Ridge Iron Ore Mine, Washington County, Missouri : origin of the rare-earth-element- and goldbearing breccia pipes /

Includes bibliographical references.