There are at least five prime ministers up to date that have received the Nobel Peace Prize award. If you were asking for the first one who received it, the answer would be Hjalmar Branting: Prime Minister of Sweden who received the Nobel award in 1921 for supporting the establishment of the League of Nations, and promoting international cooperation between countries. Lester Pearson, Prime Minister of Canada in the 1950's seems like a popular search result as well. He received the award in 1957.
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Answer:
The Constitution can be changed if an amendment is approved by 2/3 majority vote, both in the House of Representatives and the Senate.
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