Table 3.

Total of documents per year.

Year	Total of Publications Used
2021	4
2020	3
2019	13
2018	6
2017	7
2016	6
2015	9
2014	3
2013	2
2012	4
2010	3
2007	2
2005	3
2004	1
2002	2
2001	2
2000	4
1989	3
1983	1
1981	1
1978	1