To research documentation within the UN, one should be aware of the document symbols each branch of the UN utilizes. More on the symbols can be found here.
Yale University Library has been a depository for United Nations programme since 1945. The UN depository collection includes official records of the main organs of the United Nations, periodicals, United Nations Treaty Series, United Nations Development Programme and United Nations Environment Programme publications, other generally distributed documents and publications of the United Nations, and selected sales publications.
Other United Nations depository libraries in the Northeast include Brown, Columbia, Harvard, New York University, and Princeton. Consult the complete list of United Nations depository libraries for more information. While few documents are currently distributed through the Depository Programme, there is a Depository News section that may be consulted.