m(3.4 μm)−m(4.6 μm) vs. 12 +log  O/H diagram for a sample of emission-line galaxies detected in WISE 3.4 μm (W1) and 4.6 μm (W2) bands. Galaxies with Hβ equivalent width EW(Hβ) ≥ 50 Å and with L(Hβ) ≥ 3 × 10⁴⁰ erg s^-1 are shown by red filled circles while galaxies with EW(Hβ) < 50 Å and with L(Hβ) < 3 × 10⁴⁰ erg s^-1 are shown by blue open circles. Galaxies with m(3.4 μm)−m(4.6 μm)≥ 2 mag from this paper are shown by large black filled circles and from Griffith et al. (2011) by asterisks. Only the galaxies where the errors in [O iii] λ4363 emission-line flux do not exceed 50% are shown.