Left: observed quasar composite spectra compared with the predicted continuum in the MTBB model with different temperature parameters (labels in units of 10³ K) for a Schwarzschild black hole (solid) and for a maximum rotating Kerr BH (dotted). Right: the same as left, but for corrected model curves of the CMTBB model. The dashed vertical lines indicate the positions of continuum windows. References: 1 – Scott et al. (2004); 2 – Shull et al. (2012); 3 – Telfer et al. (2002); 4 – Brotherton et al. (2001); 5 – Meusinger et al. (2011); 6 – Vanden Berk et al. (2004); 7 – Francis et al. (1991); 8 – Kishimoto et al. (2008).