Text and Data Mining valid from 2018-04-23
Received: 5 February 2018
Accepted: 17 April 2018
First Online: 23 April 2018
Compliance with ethical standards
: The authors declare that they have no conflict of interest.
: Research involving human participants was done post-approval in accordance with the ethical standards of the institutional review board and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: For this kind of study, formal consent is not required.