Narcotic drugs : additional cooperative arrangements to curb illegal traffic : agreement between the United States of America and Mexico amending the agreements of August 9, 1976 and February 4, 1976, as amended, effected by exchange of letters signed at Mexico September 30, 1976. (Dept. of State : for sale by the Supt. of Docs., U.S. Govt. Print. Off., 1977)