Circular years 2008 2007 2006 2005 2004 2003 2002 2001 2000 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986 1985 1984 1983 1982 1981 1980 1979 1978 1977 1976 1975 1974 1973 1972 1971 1970 1969 1968 1967 1966 1965 1964 1963 1962

Circular No. 265, dated 11-4-1980

Circular No. 266, dated 24-4-1980

Circular No. 267, dated 24-4-1980

Circular No. 268, dated 28-4-1980

Circular No. 269, dated 29-4-1980

Circular No. 270, dated 26-5-1980

Circular No. 271, dated 26-5-1980

Circular No. 272, dated 27-5-1980

Circular No. 273, dated 3-6-1980

Circular No. 274, dated 28-6-1980

Circular No. 275, dated 16-7-1980

Circular No. 276, dated 19-7-1980

Circular No. 277, dated 21-7-1980

Circular No. 278, dated 26-8-1980

Circular No. 280, dated 20-9-1980

Circular No. 281, dated 22-9-1980

Circular No. 282, dated 22-9-1980

Circular No. 283, dated 25-9-1980

Circular No. 284, dated 13-10-1980

Circular No. 285, dated 21-10-1980

Circular No. 286, dated 17-11-1980

Circular No. 287, dated 4-12-1980

Circular No. 288, dated 22-12-1980

Circular No. 289, dated 29-12-1980