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Article History

Received: 26 November 2019

Revised: 3 December 2019

Accepted: 3 December 2019

First Online: 21 December 2019

Compliance with Ethical Standards

:

: Jiyoung Wang, Won Jun Kang, and Hojin Cho declare that they have no conflict of interest. There is no source of funding.

: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee.

: The institutional review board of our institute approved this retrospective study, and the requirement to obtain informed consent was waived.