Line widths (FWHM) and rest-frame EWs of Lyα of SHELLQs quasars. Left panel: CDF of FWHM(Lyα) in units of kilometres per second. Seven objects show unresolved lines that have an upper limit on FWHM of 230 km s⁻¹. The dotted line indicates the dividing line at 500 km s⁻¹ below which narrow-line objects are defined. Right panel: CDF of EW(Lyα). The dotted line indicates 250 Å, above which five outliers in Fig. 2, including the four Chandra targets, are found.