Text and Data Mining valid from 2019-02-07
Received: 2 August 2018
Accepted: 22 January 2019
First Online: 7 February 2019
Compliance with ethical standards
: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.