Bestandslücken
[N=1950,7-12; 1953,7; 1954,10; 1955,10; 1956,7,11,12; 1957,1-10; 1958,10; 1959,4-6; 1961,1; 1965,1,3,4,7,9-12; 1966,5,6; 1967,5,6,9,11,12; 1968,1-12; 1969,1-7,9-12; 1970,1-7,9,11,12; 1971,9,10; 1972,2,4-8,10; 1973,2,8,11,12; 1974,2,4,8; 1975,4,10-12; 1976,1-3,5-7,9; 1977,1,3,7-9,11,12; 2000,6; 2001,5-6; 2002,1-3,6; 2003; 2004,5-6; 2005; 2010,5; 2014,4; 2015,3-6; 2019,2; 2021,4]