Contour with reddish levels represents the same results shown in top panel of Fig. 1 after considering periodic obscurations in assumed sub-pc BBHs. Pluses in blue represent the results from the 3000 newly created artificial f_λ after considering E₁(B − V, ϕ)  =  E₂(B − V, ϕ)  =  E₀ with E₀ as a random value between 0 and 0.5. The solid red line shows the dependence determined from SDSS quasars as shown in top panel of Fig. 1.