Relations between equivalent widths of the [O III] λ5007 emission line and extinction-corrected (a) O₃₂ = [O III] λ5007/[O II] λ3727 and (b) Ne3O2 = [Ne III] λ3868/[O II] λ3727 for samples of CSFGs and high-z SFGs. The solid lines are the maximum likelihood relations, whereas the green line in (a) is the relation for z ∼ 1.4–3.8 galaxies (Reddy et al. 2018). LAEs at z ∼ 3 by Nakajima et al. (2020) are shown in (a) by black-filled circles. The meanings of symbols for SDSS CSFGs are the same as in Fig. 1.