Photoionization models for extreme Lyα λ1216 and Hell λ1640 line ratios in quasar halos, and PopIII vs. AGN diagnosticsA. Humphrey, M. Villar-Martín, L. Binette and R. RajA&A, 621 (2019) A10DOI: https://doi.org/10.1051/0004-6361/201732007
