Rong, Xuejing
Yin, Jia
Duan, Shuoyun
Sun, Qiang
Babar, Zaheer-Ud-Din
Article History
Received: 2 January 2020
Accepted: 21 April 2020
First Online: 29 April 2020
Ethics approval and consent to participate
: We gained approval from Centralized bidding procurement and supply chain system in Shandong to access the datasets used in the study and publish academic articles.
: Not applicable.
: The authors declare that they have no competing interests.