Observation of the Er3+ Ɖ8 groundstate ESR-resonance in YAl2 single crystals K. Baberschke, B. Bachor, H. Luft et J. Pellisson J. Phys. Colloques, 40 C5 (1979) C5-51-C5-53 DOI: 10.1051/jphyscol:1979520