Bestandslücken
[N=3.1991,2,4,6,8,12;4.1992,1,3,5-6,8,10,12;5.1993,2,4,6,8,10,12;6.19948,10,12;7.1995,4,6;8.1996,4,7;9.1997,2,4,8,10,12;10.1998,2,6,8,10,12;11.1999,2,4,6,8,10,12;12.2000,2,4,6,8-9,12;13.2001,2,4,12;14.2002,2,4,6,8,10,12;15.2003,2,4,6,8,10]