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Article History

Received: 2 February 2017

Accepted: 8 March 2017

First Online: 22 March 2017

Compliance with ethical standards

:

: All authors declare that they have no conflict of interest.

: All procedures performed in studies 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 considers that this study (retrospective study) does not require informed consent.