Text and Data Mining valid from 2018-02-01
Received: 4 May 2017
Revised: 5 November 2017
Accepted: 19 December 2017
First Online: 1 February 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of our institutional committee and with the 1964 Helsinki declaration and its later amendments.
: Informed consent was obtained from all individual participants included in the study.