Received: 5 January 2018
Accepted: 21 August 2018
First Online: 20 October 2018
Ethics approval and consent to participate
: This was a systematic review of the literature. Ethical approval and consent to participate is not applicable for such a study design.
: All authors have read and agree with the contents of this work, and have provided consent to publish.
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.