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Number of included papers (n = 290) by publication year.
| 2001 | 2002 | 2003 | 2004 | 2005 | 2006 | 2007 | 2008 | 2009 | 2010 | 2011 | 2012 | 2013 | 2014 | 2015 | 2016 | 2017 1 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 1 | 1 | - | 1 | 3 | 7 | 4 | 7 | 6 | 7 | 8 | 17 | 37 | 46 | 59 | 85 |
1 Six papers were dated 2018 but had been published online previously and were categorized as 2017.
