Text and Data Mining valid from 2019-02-26
Received: 12 December 2018
Revised: 15 February 2019
Accepted: 18 February 2019
First Online: 26 February 2019
Compliance with ethical standards
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: The study has been approved by the University Ethics Committee and has been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki.