8[1]Skill Information Services Ltd. The Economics of Rare Earth and Yttrium [M]. Eleventh Edition, 2001.
9[2]Hedrick J B. Mineral Commodity Summaries-Rare Earth [M].U.S. Geological Survey, 1996 - 2001.
10[4]Huang Wenmei, Huang Xiaowei. RE separation and attainment of high purity products in China [ A ]. RAte Earths Conference in Rio De Janeiro [C]. Brazil, 1998.
