Distribution of the z ≃ 3 quasar sample in the Γ₁ − Γ₂ plot, where Γ₁ and Γ₂ are the slopes of a power law in the log(ν)−log(νF_ν) plane in the 0.3−1 μm and 1450−3000 Å intervals (see Sect. 2.1), respectively. The red stars represent the Γ₁ − Γ₂ values of the quasar SED by Richards et al. (2006) with increasing dust reddening (following the extinction law of Prevot et al. 1984), with E(B − V) in the range 0−0.1. All quasars are within E(B − V) = 0.1, as marked by the green circle. Blue, brown, and orange symbols represent X-ray-normal quasars, X-ray-weak quasars, and X-ray-weak candidates, respectively, following the definition in Sect. 2.3. The triangle, pentagon, and square symbols mark the radio-bright (J0900+42), BALs (J1148+23, J0945+23), and reddest (J1459+00) quasars in the sample.