Text and Data Mining valid from 2019-02-18
Received: 14 October 2018
Accepted: 12 February 2019
First Online: 18 February 2019
Compliance with ethical standards
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: The study protocol was approved by the local institutional ethics committee and have therefore been performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
: All persons gave their informed consent prior to their inclusion in the study.