<Li> World Tourism Organization (UNWTO) </Li> <Li> International Refugee Organization (IRO); ceased to exist in 1952 </Li> <P> Some organizations have a relationship with the UN defined by an arrangement different from the agreements between the specialized agencies and the UN, which are establish under Articles 57 and 63 of the United Nations Charter . </P> <P> The IOM, established in 1951, is the leading inter-governmental organization in the field of migration and works closely with governmental, intergovernmental and non-governmental partners . IOM works to help ensure the orderly and humane management of migration, to promote international cooperation on migration issues, to assist in the search for practical solutions to migration problems and to provide humanitarian assistance to migrants in need, including refugees and internally displaced people . In September 2016, IOM joined the United Nations System as a related organization during the United Nations General Assembly high - level summit to address large movements of refugees and migrants . </P>

What are the six main bodies of the united nations