Funding for this research was provided by:
Hong Kong Research Grant Council (14122415, 14160516, 14177617, AoE/M-05/12, AoE/M-403/16)
Text and Data Mining valid from 2018-02-08
Received: 11 September 2017
Accepted: 17 January 2018
First Online: 8 February 2018
: The authors declare that they have no competing interests.
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