We would like to thank Pan Deng and Keling Chen for helpful discussions about similarity-weighted semblance, Jiang Yuan, Zhaoyu Jin, Ray Abma, Min Zhou, Araz Mahdad and Sergey Fomel for inspiring discussions about simultaneous-source acquisition. We also thank Ingo Grevemeyer, and two anonymous reviewers for constructive suggestions that improve the original manuscript greatly. This work is partially supported by the National Natural Science Foundation of China (Grant No.41274137), the National Science and Technology of Major Projects of China (Grant No. 2011ZX05019-006), National Engineering Laboratory of Offshore Oil Exploration, and the Texas Consortium for Computational Seismology (TCCS).