Bestandslücken
[N=27.1990,3-9; 28.1991,3; 31.1994,11,12; 32.1995,1,3-5,7-9; 33.1996,1-5,7-12; 34.1997,2-7,9,11-12; 35.1998,1-4,6-8,10-11; 36.1999,11-12; 37.2000,1,5; 40.2003,10,12; 43.2006,10; 44.2007,5,10; 45.2008,7; 49.2012,1; 50.2013, 2-3; 52.2015, 4; 53.2016,2-3]