Funding for this research was provided by:
Российский Фонд Фундаментальных Исследований (РФФИ) (18 - 02 -00269a)
Text and Data Mining valid from 2019-08-22
Received: 4 July 2019
Accepted: 10 August 2019
First Online: 22 August 2019
Compliance with ethical standards
: The authors declare that they have no conflicts of interest.