A referendum on joining the European Community was held in Norway on 25 September 1972. After a long period of heated debate, the "no" side won with 53.5% of the vote. Prime Minister Trygve Bratteli, who had championed a "yes" vote, resigned as a result. This was Norway's second attempt at becoming a member, after having been vetoed by France in January 1963 and again temporarily in 1967, but the first attempt with a referendum on a set of fully negotiated accession terms.
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Text from the Wikipedia article “Norwegian European Communities membership referendum”, available under CC BY-SA 4.0.