Text and Data Mining valid from 2018-08-15
Received: 22 June 2018
Accepted: 24 July 2018
First Online: 15 August 2018
Ethics approval and consent to participate
: The need for informed consent was waived by the institutional review board of Cheil General Hospital because of the retrospective nature of the study.
: Not applicable
: The authors declare that they have no competing interests.
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