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Article History

Received: 20 November 2017

Accepted: 5 March 2018

First Online: 27 March 2018

Ethics approval and consent to participate

: This study did not require the approval of an ethics committee as it is a secondary analysis of a database of a public domain and of free access.

: This study did not require consent for publication.

: The authors declare that they have no competing interests.

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