Text and Data Mining valid from 2019-01-02
First Online: 2 January 2019
Compliance with Ethical Standards
: The author declares that he has no conflict of interest.
: All procedures performed in this study did not involve any human participants, and the data retrieved were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Declaration of Helsinki and its later amendments or comparable ethical standards. For this type of study, formal consent is not required.