1. Spectra and Energy Levels of Rare Earth Ions in Crystals;Dieke,1968
2. Optical Spectra of Transparent Rare Earth Compounds;Hufner,1978
3. Laser Crystals;Kaminskii,1981
4. A Systematic Analysis of the Spectra of the Lanthanides Doped into Single Crystal LaF3;Carnall;Argonne National Laboratory Report No. ANL-88-8,1988