Bestandslücken
[N=21.1996,3; 22.1997,1,5,10,11; 23.1998,3,10; 24.1999,9-10,12; 25.2000,5,12; 26.2001,3; 27.2002,1-4,9,11-12; 29.2004,1-2; 30.2005,5,8-9,12; 31.2006,1,9; 32.2007,2,8,11; 33.2008,6; 34.2009,10; 37.2012,2,4-12; 38.2013,1-7,9; 39.2014,4-5; 40.2015,2,4,6,8,9,11; 41.2016,2]