Received: 3 July 2018
Accepted: 30 October 2018
First Online: 16 November 2018
Ethics approval and consent to participate
: The study was reviewed and approved by the Institutional Review Board, Singapore, provenance and peer review is not commissioned, externally peer reviewed (reference no: 2017/008700).
: Not applicable.
: The authors declare that they have no competing interests.
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