[Ren, Teng] Cent South Univ Forestry & Technol, Sch Logist & Transportat, Changsha 410004, Hunan, Peoples R China.
[Li, Sidi] Cent South Univ Forestry & Technol, Sch Tourism Management, Changsha 410004, Hunan, Peoples R China.
[Zhang, Xinguang] Yantai Univ, Sch Math & Informat Sci, Yantai 264005, Shandong, Peoples R China.
[Zhang, Xinguang; Liu, Lishan] Curtin Univ Technol, Dept Math & Stat, Perth, WA 6845, Australia.
[Liu, Lishan] Qufu Normal Univ, Sch Math Sci, Qufu 273165, Shandong, Peoples R China.