Text and Data Mining valid from 2019-10-31
Received: 17 June 2019
Revised: 7 October 2019
Accepted: 10 October 2019
First Online: 31 October 2019
Compliance with ethical standards
: The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the paper. The authors declare that they have no conflict of interest.