Funding for this research was provided by:
Research Council at University of Macau (MYRG2017-00173-FSS)
Received: 12 April 2019
Accepted: 18 October 2019
First Online: 27 November 2019
Ethics approval and consent to participate
: Ethical Approval is not needed because it is a systematic review article. Informed consent forms from participants are unnecessary, because in our manuscript we selected the studies that already gained approval from participants.
: Not Applicable.
: The authors declare that they have no competing interests.