Text and Data Mining valid from 2019-11-02
Received: 8 July 2019
Accepted: 21 October 2019
First Online: 2 November 2019
Compliance with ethical standards
: The authors declare that they have no competing interests.
: No funding has been received for this study.
: Ethical approval was obtained by the institutional review board at the Yonsei Sarang Hostpital.