| Year |
| ||||||||
2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | Total | |
The total amount of literature | 25 | 25 | 20 | 20 | 25 | 23 | 27 | 29 | 39 | 233 |
Effective number of papers | 24 | 23 | 20 | 19 | 24 | 22 | 24 | 28 | 35 | 219 |