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This work is excerpted from an official document of the United Nations. Prior to 17 September 1987 it was the policy of this organisation to not seek copyright, keeping most of its documents in the public domain, in order to disseminate "as widely as possible the ideas (contained) in the United Nations Publications" (detail).

UN works not in the annex to Administrative Instruction ST/AI/189/Add.9/Rev.1 (available in English) published in the US before 1978 are in the public domain because they were published without a copyright notice. UN works not in the annex to ST/AI/189/Add.9/Rev.1 published in the US between 1978 and 17 September 1987 are in the public domain because they were published without a copyright notice and their copyright was not subsequently registered with the U.S. Copyright Office within 5 years (from 1978 through 1993 the UN did not register any document published in the US before 17 September 1987).

This work is in the public domain in the United States because it meets two requirements:

1. it was published in the United States before 17 September 1987 by the United Nations, and
2. it is not sourced to a document listed in the appendix of ST/AI/189/Add.9/Rev.1 (these documents were copyrighted under an exception to the general practice).

This work is copyrighted in jurisdictions that do not apply the rule of the shorter term for US works or that specifically extend local copyright protection to works of the U.N.