Holdings
10.1956 - 21.1966; 23.1968,4-5; 25.1970 - 27.1972; 32.1977,4; 36.1981,1; 39.1984; 51.1997,2,5; 52.1998,5; 57.2003 - 58.2004,1-7,9
Holdings gaps
[N=1958,4,6-8,10-12; 1959,1-2,8-9; 1960,1,6; 1961,3; 1965,9; 1966,1-7,9-12; 1970,1-3,10-12; 1971,2-6,12; 1972,1-7,11; 2003,10]