Example spectra of O32 emitters in our sample. The upper panel shows the spectrum of the galaxy with the most extreme oxygen ratio (dust-corrected O32 = 23) from the UDF-mosaic catalogue with id = 6865 and z = 0.83. The orange shaded lines show the Hγ, Hβ, and [O III]λλ4959,5007 of neighbouring sources at z ≈ 0.62. An example spectrum of a galaxy with a lower O32 ratio, in this case with dust-corrected O32 = 0.25, is shown in the lower panel (UDF-mosaic, id = 892, z = 0.74).