Received: 8 October 2017
Accepted: 19 December 2018
First Online: 1 February 2019
Ethics approval and consent to participate
: Ethics approval and participant consent was not necessary as this study involved the use of a previously-published de-identified database according to the decree law n. 196 of 30 June 2003.
: Unidentifiable participants.
: The authors declare that they have no competing interests.
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