Text and Data Mining valid from 2018-02-05
Received: 11 October 2017
Accepted: 19 January 2018
First Online: 5 February 2018
Change Date: 4 June 2018
Change Type: Correction
Change Details: A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
: The authors declare that they have no competing interests.