Text and Data Mining valid from 2019-08-23
Received: 23 April 2019
Accepted: 5 August 2019
First Online: 23 August 2019
Ethics approval and consent to participate
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The local institutional review board approved this retrospective study and waived the requirement for informed consent.
: All authors provide their consent for publication.
: The authors declare that they have no competing interests.