Top panel: relation between log(He II/Hβ) and the total oxygen abundance calculated using HCM for objects of the control sample both with the emission-line at [O III] λ4363 Å (filled symbols) and without it (empty symbols). Different symbols represent galaxies with a detected bump of WR stars (blue triangles) or without one (orange circles). Bottom panel: histogram of the 12 + log(O/H). The black line corresponds to the oxygen abundance distribution for the whole sample, while blue and orange hatched histograms represent the oxygen abundance distributions for WR and nonWR galaxies, respectively.