Distribution of log(Hα_br/Hβ_br) for our sources with available data. The mean values from other literature samples (Osterbrock 1977, O77, Neugebauer et al. 1979, N79, Goodrich 1990, G90, Greene & Ho 2005, GH05, Zhou et al. 2006, Z06, Dong et al. 2007, D07, Mejía-Restrepo et al. 2022, MR22, Ma et al. 2023, M23) are also shown for reference according to the colour code. The mean of our values is shown in black. The BASS sample described in Mejía-Restrepo et al. (2022) has been split according to the column density N_H inferred from the X-ray analysis.