Text and Data Mining valid from 2018-06-12
Received: 22 September 2017
Accepted: 30 May 2018
First Online: 12 June 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: No ethical approval was required for this study, since no human participants or animals were used in this study.
: Formal consent is not required for a systematic review and meta-analysis.