Funding for this research was provided by:
National Natural Science Foundation of China (61572155, 61672188 and 61272386)
the MOE–Microsoft Key Laboratory of Natural Language Processing and Speech
the Major State Basic Research Development Program of China (2015CB351804)
Text and Data Mining valid from 2018-05-24
Received: 7 January 2018
Accepted: 20 April 2018
First Online: 24 May 2018
: The authors declare that they have no competing interests.
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