Funding for this research was provided by:
Text and Data Mining valid from 2018-04-16
First Online: 16 April 2018
Compliance with Ethical Standards
: Liia Kivelä, Marinos Rodolfos Papadopoulos, and Niki Antypa declare no conflicts of interest.
: This article does not contain any studies with human or animal subjects performed by any of the authors.