Text and Data Mining valid from 2019-08-08
Received: 29 May 2019
Accepted: 1 August 2019
First Online: 8 August 2019
Compliance with ethical standards
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: The study was conducted according to the principle of Declaration of Helsinki.
: For this type of study, formal consent is not required.