Text and Data Mining valid from 2019-11-26
Received: 5 June 2019
Accepted: 22 September 2019
First Online: 26 November 2019
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: Not applicable. The information used to perform this review is available online and it is public. Therefore, the analysis performed in this study is in accordance with the ethical standards.
: For this type of study, formal consent is not required.