Zhong, Chenwen
Kuang, Li
Li, Lina
Liang, Yuan
Mei, Jie
Li, Li
Funding for this research was provided by:
the National Natural Science Foundation of China (71673311)
the Health and Family Planning Commission of Guangdong Province
Article History
Received: 21 December 2017
Accepted: 10 April 2018
First Online: 27 April 2018
Ethics approval and consent to participate
: Informed oral consent was obtained from all participants. Ethical approval for the study was obtained from the Institutional Review Board of the School of Public Health, Sun Yat-Sen University, P.R. China. The protocol for this study conforms to the guidelines of the 1975 Declaration of Helsinki.
: The authors declare no conflicts of interest.
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