Funding for this research was provided by:
National Natural Science Foundation of China (81460490)
Project for Developing Top Western Disciplines in University (NXYLXK2017B08)
the Important Research Topic of Health and Family Planning Commission of Ningxia (2017-NW-018)
Text and Data Mining valid from 2019-04-03
Received: 4 October 2018
Accepted: 27 March 2019
First Online: 3 April 2019
Ethics approval and consent to participate
: The study was approved by the Medical Ethics Committee of Ningxia Medical University (No.2014–090), and oral consent was obtained from participants prior to the interview.
: Not applicable.
: The authors declare that they have no competing interests.
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