Bestandslücken
[N=1970,1-6, 8-12; 1971,1-2, 4-12; 1972,1-4, 6-12; 1973 - 1974; 1975,2-12; 1976,1-6, 8-11; 1977,2, 4, 6-12; 1978,1-7, 12; 1979,7-12; 1980, 1,12; 1981 - 1982; 1983,1-6, 8-12; 1984,2; 1989,2-6; 1990,1-5; 1991,3; 1992,4; 1995,6; 2000,2; 2003,4; 2018,3-4]