Stacked composite spectrum of all QSOs in our golden sample. We show the mean composite spectrum (teal solid line) and bootstrap 1σ interval (shaded region). The shaded gray regions mark the rest-frame wavelength intervals used to fit a power-law continuum. We represent the fitted power law as a dashed red line, whose slope is β_UV = −1.55 ± 0.02. We show the labels of the most important QSO emission lines and the LyC limit (91.2 nm).