Five referendums were held in Switzerland in 1891.
 The first was held on 15 March on a federal law on federal officials who had become unemployable due to disability, and was rejected by 79.4% of voters.
 The second was held on 5 July on a constitutional amendment, and was approved by 60.3% of voters.
 Two referendums were held on 18 October, one on revising article 39 of the federal constitution and one on a federal law on Swiss tariffs; both were approved.
 The last was held on 6 December on the question of whether the federal government should purchase the Swiss central railway, but was rejected by 68.9% of voters.
Five referendums were held in Switzerland during 1950.
 The first was held on 29 January on extending a federal resolution on promoting housebuilding, and was rejected by voters.
 The second was held on 4 June on the federal budget, and was also rejected by voters.
 The third was held on 1 October on a popular initiative "for the protection of ground and labour by prohibiting speculation", and was rejected by voters.
 The final two were held on 3 December on revising article 72 of the constitution regarding the election of the National Council and a federal resolution on financial order between 1951 and 1954.
 Both were approved by voters.
Nine referendums were held in Switzerland during 1996.
 The first five were held on 10 March on revising article 116 of the Swiss Federal Constitution regarding language, abolishing the cantons' responsibilities for providing army equipment, abolishing the federal requirement to purchase distilling equipment, abolishing federal financing of parking areas at rail stations, and whether municipality of Vellerat (then part of the canton of Bern) should become part of the canton of Jura.
 All proposals except the one regarding army equipment were approved.
The Federal Constitution of the Swiss Confederation (SR 10, German: "Bundesverfassung der Schweizerischen Eidgenossenschaft (BV)" , French: "Constitution fédérale de la Confédération suisse (Cst.)"
 , Italian: "Costituzione federale della Confederazione Svizzera (Cost.)"
 , Romansh: ' ) of 18 April 1999 (SR 101"') is the third and current federal constitution of Switzerland.
 It establishes the "Swiss Confederation" as a federal republic of 26 cantons (states).
 The document contains a catalogue of individual and popular rights (including the right to call for popular referenda on federal laws and constitutional amendments), delineates the responsibilities of the cantons and the Confederation and establishes the federal authorities of government.
Five referendums were held in Switzerland during 1931.
 The first was held on 8 February on a federal resolution on a petition for a referendum on article 12 of the constitution concerning bans on religious orders, and was approved by a majority of voters and cantons.
 The second and third were held on 15 March on revising article 72 of the constitution concerning the election of the National Council and on revising article 76, 96 and 105 on the legislative term.
 Both were approved.
 The fourth and fifth were held on 6 December on a federal law on aged and bereavement insurance and a federal law on tobacco taxation.
 Both were rejeected.
Four referendums were held in Switzerland during 1921.
 The first two were held on 30 January on holding referendums on treaties that would be valid for at least 15 years and on abolishing the military judiciary.
 The treaty proposal was approved, whilst the abolishment of the military judiciary was rejected.
 The third and fourth were held on 22 May on add articles 37bis and 37ter on road traffic and aviation to the constitution, and on only adding article 37ter on aviation.
 Both were approved.
Three referendums were held in Switzerland during 1898.
 The first was held on 20 February on a federal law that would nationalise the railways, and was approved by a majority of voters, leading to the establishment of Swiss Federal Railways in 1902.
 The second and third referendums were held on 13 November on revising article 64 and adding article 64bis to the constitution, both of which were approved by a majority of voters and cantons.
Four referendums were held in Switzerland during 1957.
 The first two were held on 3 March on a federal resolutions on introducing two new articles to the federal constitution; 22bis concerning civil protection and 36bis on radio and television.
 Both were rejected.
 The third and fourth were held on 24 November on introducing another article to the constitution (24 quinquies concerning nuclear power and protection from radiation) and a federal resolution on prolonging the federal breadstuffs law.
 Both were approved.
Six referendums were held in Switzerland during 2006.
 The first was held on 21 May on revising article 48a in the Swiss Federal Constitution on education, and was approved by 86% of voters.
 The second set of three referendums was held on 24 September on proposed amendments to the laws on asylum and foreigners, as well as a popular initiative on diverting profits from the Swiss National Bank into the national pension fund.
 The two laws were approved, whilst the initiative was rejected.
Four referendums were held in Switzerland during 1949.
 The first two were held on 22 May on revising article 39 of the federal constitution concerning the Swiss National Bank and a federal law amending a 1928 law on measures against tuberculosis, with both rejected by voters.
 The third was held on 11 September on a popular initiative "for the recurrence to direct democracy" and was narrowly approved.
 The final one was held on 11 December on a federal law to amend the employment status of federal civil servants, and was also approved.

Question: Four referendums were held in Switzerland during 1949, the first two were held on 22 May on revising article 39 of which third and current federal constitution of Switzerland?
Answer: Federal Constitution of the Swiss Confederation