Bestandslücken
[N=1973,2u.11-12; 1974,2-9; 1975,5u.7; 1976,11-12; 1977,5-6u.8; 1978,12; 1980,8-9; 1981,2-3u.5-12; 1982,1u.3-4u.6u.8-12; 1984,1; 1986,5; 1987,4; 1988,9; 1989,6u.10u.12; 1990,2u.5; 1992,2u.8; 1993,3u.5u.7u.9; 1994,6u.9u.12; 1995,5u.7; 1996,1u.3u.12; 1997,3u.7u.11; 1998,7-8u.12; 1999,2-3u.8u.11; 2000,1u.3; 2001,7-8u.10; 2006,6-7; 2010,1-3u.5u.7-12; 2011-2012; 2013,1-3u.5u.7-12; 2014,2-4u.6-8u.10-12; 2017,3; 2018,4]