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Article History

Received: 1 June 2018

Revised: 22 July 2018

Accepted: 23 August 2018

First Online: 1 September 2018

Compliance with ethical standards

:

: The 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. For retrospective study, formal consent is not required.

: Opt-out consent method was chosen, approved by the institutional review board of Yokohama City University because no information identifying individual participants was involved in this article.