Distributions of the X-ray-selected BCU sample in one-dimensional and two-dimensional planes of ﹩{\rho }_{{\rm{s}}}﹩ and ﹩\mathrm{log}{\nu }_{{\rm{s}}}﹩. Comparisons of the ﹩\mathrm{log}{\nu }_{{\rm{s}}}﹩ distributions for BL Lac candidates and FSRQ candidates picked up with our method with different subclasses of FSRQs and BL Lacs from the reference sample are also shown in the upper panel.