“…Examples focusing on the concept of σ-convergence includeLyons (1991),Chen and Fleisher (1996),Tsui (1996),Raiser (1998),Zheng et al (2000),Chang (2002),,Duan (2008),Zou et al (2008),Zhou and Zou (2010). For the studies of β-convergence, seeChen and Fleisher (1996),Jian et al (1996), Gunlach (1997,Raiser (1998),Tian (1999),Chen and Feng (2000),Choi and Li (2000),Dacosta and Carroll (2001),Yao and Zhang (2001a),Yao and Zhang (2001b),Cai et al (2002),Yao and Zhang (2002),Weeks and Yao (2003),Wu (2004),Duan (2008),Hao (2008),Li and Xu (2008),Zou et al (2008),Villaverde et al (2010),Gries and Redlin (2011),Marti et al (2011). For more detailed literature reviews, seeWu (2004) andCheong (2012).…”