In general, UN documents should be cited in the following order: author, 'title' (date) document number.
UNSC Res 1373 (28 September 2001) UN Doc S/RES/1373
UNGA 'Report of the Special Committee on Principles of International Law Concerning Friendly Relations and Cooperation Among States' UN GAOR 25th Session Supp N° 18 UN Doc A/8018 (1970)