Funding for this research was provided by:
Taishan Scholar Foundation of Shandong Province
Natural Science Foundation of Shandong Province (ZR2019BC064)
Text and Data Mining valid from 2019-01-28
Received: 23 November 2018
Accepted: 21 January 2019
First Online: 28 January 2019
Compliance with Ethical Standards
: Zhengzong Wu declares that he has no conflict of interest.
: This article does not contain any studies with human or animal subjects.
: Informed consent was obtained from all individual participants included in the study.