Equivalent width of the [OI]λ6300 line versus the instrumental flux of the continuum at 6300Å. Detections are shown as red filled diamonds, while upper limits of nondetections (taken as 3σ times the average FWHM of detections in our sample) are shown as black open diamonds. Right panel: A1 configuration, which was observed four times and has better S/N, left panel: all other configurations.