Examples of the spectral decomposition (top panels) and the model fitting (bottom panels) to the broad emission lines Lyα+N V (left), C IV (middle), and C III](right). Top panels: observed spectra (gray curves) are fitted by three components, i.e., a power law continuum (green), a Gaussian broad-line component (blue, for Lyα+N V we use two broad Gaussian components, with the separation of the two line peaks fixed at 6000 km s⁻¹), and multiple lines from the Sigut et al. (2004) Fe II templates (magenta). Bottom panels: gray curves show the broad-line profiles with the continuum and Fe II lines subtracted. The red lines represent the best BLR model fitting results as introduced in Sect. 2.2.