[1] Shaanxi Normal Univ, Northwest Inst Hist Environm & Socio Econ Dev, Xian, Shaanxi, Peoples R China
[2] Nanjing Agr Univ, Coll Econ & Management, Nanjing, Jiangsu, Peoples R China
[3] Shaanxi Normal Univ, Northwest Inst Hist Environm & Socio Econ Dev, Changan Campus 620,West Changan Ave, Xian 710119, Peoples R China