Text and Data Mining valid from 2019-07-31
Received: 18 March 2019
Accepted: 18 July 2019
First Online: 31 July 2019
Compliance with ethical standards
: Author Fangfang Wu, Xiaobei Zhang, Yali Liu, Dong Cao, Yongjiang Yu, and Yuan Ma declare that they have no conflict of interest.
: All analyses were based on previous published studies, thus no ethical approval is required.
: This article does not contain any studies with human participants or animals performed by any of the authors.
: For this type of study formal consent is not required.