Document is current

Article History

Received: 15 November 2017

Accepted: 5 September 2018

First Online: 17 September 2018

Ethics approval and consent to participate

: The study was overseen by and obtained signed ethics approval from the institutional review board of the Ethics Committee at the School of Public Health, Shandong University (No. 20161103). All subjects gave voluntary verbal consent to participate in the anonymous survey after receiving an explanation of the study design and reading the questionnaire instructions prior to responding.

: Not applicable.

: The authors declare that they have no competing interests.

: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.