Text and Data Mining valid from 2019-08-15
Received: 6 December 2018
Accepted: 7 June 2019
First Online: 15 August 2019
Ethics approval and consent to participate
: Ethical approval was granted by Jiading district center for disease control and prevention research ethics committee. All subjects gave informed consent to participate in the study, they would like to participate in investigation and answer all the related questions in the questionnaire.
: Not applicable.
: The authors declare that they have no competing interests.