-Existencias: 1966 vol. 71, no. 6; 1967, vol. 72, no. 5-6; 1968 vol. 73, no. 3, 5; 1970 vol. 75, no. 2, 6; 1971 vol. 76, no. 1, 5; 1972 vol. 77, no. 1, 6; 1974 vol. 79, no. 1; 1976 vol. 81, no. 1, 4; 1977 vol. 82, no. 2-4; 1978 vol. 83, no. 2-4, 6; 1979 vol. 84, no. 1-4; 1980 vol. 85, no. 5; 1981 vol. 86, no. 1-6; 1982-1984 vol. 87-89, no. 1-4; 1985 vol. 90, no. 1-3; 1986 vol. 91, no. 3; 1987 vol. 92, no. 2