History of EU referenda

REFERENDUMS RELATED TO THE EUROPEAN UNION
https://en.wikipedia.org/wiki/Referendums_related_to_the_European_Union

This is a list of referendums related to the European Union, or its predecessors, the European Communities. Since 1972, a total of 48 referendums have been held by EU member states, candidate states, and their territories, with several additional referendums held in countries outside of the EU. The referendums have been held most commonly on the subject of whether to become a member of European Union as part of the accession process, although the EU does not require any candidate country to hold a referendum to approve membership or as part of treaty ratification. Other EU-related referendums have been held on the adoption of the euro and on participation in other EU-related policies. The United Kingdom is the only EU member state to have held referendums on the issue of continued membership of the European Union and its antecedent organisation, the European Communities. In the first referendum in 1975, continued membership of what was then the European Communities (which included the European Economic Community, often referred to as the Common Market in the UK)[nb 1] was approved by 67.2% of voters, while in its second referendum in 2016 voters voted by 51.9% to leave the European Union.[nb 2] Greenland, an autonomous territory of Denmark, voted to leave the EEC in a referendum in 1982 by 53% of voters.

Structural evolution
Main article: Treaties of the European Union The following timeline illustrates the integration that has led to the formation of the present union, in terms of structural development driven by international treaties:

https://en.wikipedia.org/wiki/European_Union