CMB radiation, could be expected and indeed is revealed here.

Working on the DGP model, the cumulative probability distributions are plotted in Fig. 6, which also locate the $\Delta A$ values with different matter density parameter. The probabilities associated with differential areas are also summarized in Table 1. Similarly, the probability of the matter density parameter $\Omega_m=0.275$ being consistent with the GP reconstructed function $\mathcal{D}_{\rm obs}$ is $99.99\%$, while the probabilities that the matter density parameter $\Omega_m=0.260$ and $\Omega_m=0.305$ being inconsistent with the current SGL observations are $90\%$. Therefore, in the framework of this modified gravity theory, the matter density parameter could be determined at the precision of of $\Delta \Omega_m \sim 0.015-0.03$. More interestingly, benefit from the redshift coverage of background sources in the lensing systems, the methodology proposed in this analysis may provide improved constraints on the DGP model, which was ruled out observationally considering the precision cosmological observational data. Such issue has been extensively discussed in many previous works [@Wang08; @Maartens10].

However, there are several sources of systematics we do not consider in the above analysis and which remain to be clarified for this methodology. **As a final remark, we discuss several possible sources of systematic errors, 