Text and Data Mining valid from 2018-02-21
Received: 25 October 2017
Accepted: 13 February 2018
First Online: 21 February 2018
Compliance with ethical standards
: Manuscript submitted for publication has been approved by the appropriate ethics committee and have, therefore, been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
: The authors have declared no conflict of interest.