Text and Data Mining valid from 2019-01-21
Received: 21 October 2018
Accepted: 4 January 2019
First Online: 21 January 2019
Compliance with ethical standards
: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2008. For this type of study formal consent is not required.
: The authors declare that they have no conflicts of interest.