Funding for this research was provided by:
National Science Foundation (1549608)
Text and Data Mining valid from 2018-07-09
Received: 18 February 2018
Accepted: 13 June 2018
First Online: 9 July 2018
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.