Liu, Tongtong
Li, Shunping http://orcid.org/0000-0001-8144-6220
Yang, Renyong
Liu, Shimeng
Chen, Gang
Article History
Received: 18 July 2018
Accepted: 3 December 2018
First Online: 3 January 2019
Ethics approval and consent to participate
: The study has been approved by the Ethics Review Board of the School of Preventive Medicine, Shandong University (Reference No. 20170301). Informed consent was obtained from all participants prior to questionnaire administration.
: Not applicable.
: The authors declare that they have no competing interests.
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