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Article History

Received: 3 July 2019

Revised: 27 September 2019

Accepted: 31 October 2019

First Online: 22 November 2019

Compliance with Ethical Standards

:

: Endel Sorra, Muhammad U Aziz, and Fangyu Peng declare no conflict of interest.

: All procedures performed in study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

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