(article 163 of the Constitution). A three-fifths majority of the membership of the Parliament is required to submit a bill to amend the Constitution to a referendum (article 164 of the Constitution). A referendum was called by the Parliament of Estonia on 2 occasions since Estonia regained independence from the USSR. a referendum on a new constitution and citizenship in 1992 Estonian European Union membership referendum in 2003 Also, there was a referendum on the restoration of Estonian independence in 1991 while Estonia was still under Soviet occupation. See also Electoral districts of Estonia Electoral calendar Electoral system Electronic voting in Estonia External links History of the RiigiKogu Adam Carr's Election Archive Parties and elections National Electoral Committee of Estonia NSD: European Election Database - Estonia publishes regional level election data; allows for comparisons of election results, 1992-2007 References