1. Recovery of rare earths from phosphorus rock by solvent extraction;Lounamaa,1980
2. The recovery of the lanthanides from phosphate rock;Habashi;J. Chem. Tech. Biotechnol.,1985
3. Recovery of rare earths from secondary sources by solvent extraction;Judin,1981
4. Contributions à la recuperation des lanthanides des phosphates naturels;Ionescu,1980
5. Extraction of sum rare-earth metals from phosphogypsum;Rusin,1980