Current trends in social relationships, strongly influenced by their increasingly international character, are resulting in a steadily growing interdependence of sovereign States. Political, economic, military and social problems have been re-examined. Organisations, economic unions, military alliances and defence agreements have been established. Free movement of persons and goods is everywhere considered to be desirable, while in the meantime the formalities to be completed on crossing frontiers have been reduced to a bare minimum. The development of tourism, which now plays an important role for three or four months in the year and which attracts all sections of the population, is equally a demonstration of a real desire for foreign contacts.