Left panel: L_2 − 10 as a function of v_CIV for the WISSH quasars (black circles). We also report hyper-luminous quasars at z = 2 − 3 (C17 sample, blue triangles). Middle panel: intrinsic α_OX as a function of v_CIV for the WISSH quasars. Red circles indicate X-ray weak sources (see Sect. 3 for details). Right panel: L₂₅₀₀ Å as a function of v_CIV. Solid and dashed lines report the best-fit linear relation and 1σ uncertainties on the normalisation for the WISSH-only relations. Dotted line in the left panel reports the best-fit relation with the addition of the C17 sample. Orange lines in the right panel report the best-fit L_2 − 10–v_CIV relation normalised to the mean values of L₂₅₀₀ Å.