1. Spectroscopic Properties of Rare Earths;Wybourne,1963
2. Operator Techniques in Atomic Spectroscopy;Judd,1963
3. Optical Spectra of Transparent Rare Earth Compounds;Hüfner,1978
4. Parametric energy level analysis of Ho3+: LaCl3
5. Lanthanide and Actinide Chemistry and Spectroscopy;Hessler,1980