Approximate polarization selection rules for the 3P0 → 3H4 transition in Pr: β" alumina single crystals P.R. NELSON, D.J. VICKERS et O.M. STAFSUDD J. Phys. IV France, 04 C4 (1994) C4-419-C4-422 DOI: 10.1051/jp4:19944100