Researching treaties to which the United States may not be a party can be a challenge. Multilateral treaties are usually the easiest, as they are published in sets like the United Nations Treaty Series (UNTS), and on various web sites. Of course, only those treaties deposited with the UN Secretary General will become part of the UNTS. Although most multilateral (and many bilateral) treaties are deposited with the UN, states are under no obligation. For more information on the role of the UN as a treaty depository, see the Summary of Practice of the Secretary-General as Depository of Multilateral Treaties on the UN website, or consult the Treaty Handbook , 4th Floor, KZ1302 .T73 2013 - both were written by the Treaty Section of the . Office of Legal Affairs. To contact the . Office of Legal Affairs, Treaty Section, call (212) 963-2523 or email them at [email protected] .