Congresses of plenipotentiaries of the contracting countries, or simple Administrative Conferences, according to the importance of the questions to be solved, are held when a demand for them is made or approved by two-thirds, at least, of the Governments or Administrations, as the case may be.
Nevertheless, a Congress must be held at least once every five years. Each country may be represented either by one or several delegates, or by the delegation of another country. But it is understood that the delegate or delegates of one country can be charged with the representation of two countries only, including the country which they represent.
In the deliberations each country has one vote only.
Each Congress fixes the place of meeting for the following Congress. For Conferences, the Administrations fix the places of meeting upon Proposal of the International Bureau.