Examples of UKIDSS sources producing a convex quadratic fit, but still satisfying the SED matching criteria of Eq. (2). Left: UKIDSS source with a flat NIR SED (and therefore most likely not being a counterpart of the corresponding R08 object) and high convexity. Right: reddened UKIDSS source that is probably the dominant counterpart of the R08 object; the slight convexity of its quadratic fit is probably produced by uncertainties or variability on the measured fluxes. The values of ⟨ R ⟩ and the quadratic coefficient a for each source are indicated at the lower right corner of each panel.