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Article History

Received: 7 August 2018

Accepted: 23 November 2018

First Online: 5 December 2018

Ethics approval and consent to participate

: The study was approved by the local ethics committee (n°5/2011, <i>A.O.U.P. “Paolo Giaccone”</i>, Palermo, Italy).

: Written informed consent was provided by parents of all participants.

: All authors declare that they have no competing interests.

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