(a) and (b) Relations between the Lyα escape fraction f_esc(Lyα) in low-redshift LyC leaking galaxies and the O₃Mg₂ = [O iii]λ5007/Mg ii λ2796+2803 ratio and the Mg₂ = Mg ii λ2796/Mg ii λ2803 ratio, respectively. (c) and (d) Relations between the LyC escape fraction f_esc(LyC) in low-redshift LyC leaking galaxies derived from the SED fits and the O₃Mg₂ and Mg₂, respectively. The galaxies from this paper and from Izotov et al. (2016a, b, 2018a, b, 2021a), Borthakur et al. (2014), Chisholm et al. (2017), Flury et al. (2022a), and Xu et al. (2022) are represented by red and blue symbols, excluding objects observed with the XShooter (Fig. 9, Guseva et al. 2020), which are shown by black symbols. LyC leakers and galaxies with upper limits of LyC emission are shown by filled circles and open circles with downward arrows, respectively. Error bars in black (all panels) represent average 1σ deviations, whereas error bars in cyan and magenta [panels (b) and (d)] are minimal and maximal 1σ errors of Mg₂ for the SDSS+XShooter sample, respectively. The values of O₃Mg₂ and Mg₂ for all galaxies are calculated in this paper.