Bestandslücken
[N=1980,5; 1981,10; 1984,6; 1985,3u.5; 1987,4u.12; 1988,9; 1990,11; 1991, 6u.8u.11-12; 1992,10u.12; 1993,3u.9-11; 1994,5; 1995; 1996,5; 1997,6u.11-12; 1998,5u.7-8; 1999; 2000,1-3u.5-8u.11; 1999,1-3u.12; 2000,4-5u.9-12; 2001,1-3u.5u.7-8; 2002,2; 2008,9; 2015,12; 2016,3u.6u.10-11; 2017,1-2u.4]