Panel a: distribution of differences between oxygen abundances 12 + log O/H derived by the semi-empirical and the direct methods for the sample from Table A.2 excluding galaxies with non-detected [O III]λ4363 Å emission lines. Panel b: as in panel a but for differences between 12 + log O/H derived by our new strong-line and the direct methods. Panel c: as in panel a but for differences between 12 + log O/H derived by the strong-line and the semi-empirical methods for all SFGs from Table A.2. Panel d: as in panel c but for differences between 12 + log O/H derived by the strong-line method and the strong-line method by Yin et al. (2007). Panel e: as in panel c but for differences between 12 + log O/H derived by the strong-line method and the P-method (Eq. (23) in Pilyugin & Thuan 2005). Panel f: as in panel c but for differences between 12 + log O/H derived by the strong-line method and the P-method (Eq. (24) in Pilyugin & Thuan 2005). In all panels, galaxies with observed and non-observed [O II]λ3727 emission line are shown by filled and open circles, respectively. Solid horizontal lines indicate average abundance differences and dotted horizontal lines indicate ±1σ dispersions of the sample around the average values.