Funding for this research was provided by:
Hong Kong University Grants Committee (UGC/FDS25/E09/17)
Text and Data Mining valid from 2019-12-01
Received: 8 July 2019
Accepted: 15 November 2019
First Online: 6 December 2019
: I confirm that I have read BioMed Central’s guidance on competing interests and have included a statement in the manuscript indicating that none of the authors have any competing interests.