2Clur D A, Hansen K R N. Rare Earth Recovery From Phosphogypsum : South African, ZA8005.318 [ P ]. 198 1.
3Jarosiski A, Kowalczyk J, Mazanek Cz. Development of the Polish Wasteless Technology of Apatite Phosphogypsum Utilization with Recovery of Rare Earths[J]. J Alloys Comp, 1993,200 ( 1-2 ) : 147 - 150.