Text and Data Mining valid from 2019-01-26
First Online: 26 January 2019
Compliance with Ethical Standards
: 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.
: Informed consent was obtained from the guardian of all individual participants in the study.
: All authors declare that they have no conflict of interest.