Text and Data Mining valid from 2018-12-18
Received: 10 October 2018
Accepted: 11 December 2018
First Online: 18 December 2018
Compliance with ethical standards
: The procedures performed were in accordance with the ethical standards of the institutional ethics committee and with the 1964 Helsinki declaration and its later amendments. For this type of study, formal consent is not required.
: The authors declare that they have no conflict of interest.