[Ning, Yixi;Long, Ziwu] Wuhan Polytech Univ, Sch Econ & Management, Wuhan, Hubei, Peoples R China.^[Ning, Yixi] Univ Houston Victoria, Sch Business Adm, Victoria, TX 77901 USA.^[Xu, Gubo] Anhui Open Univ, Coll Econ & Management, Hefei, Anhui, Peoples R China.