ABBA was a Swedish pop group formed in Stockholm in 1972 by Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. They are one of the most popular and successful musical groups of all time, and are one of the best-selling music acts in the history of popular music. In 1974, ABBA were Sweden's first winner of the Eurovision Song Contest with the song "Waterloo", which in 2005 was chosen as the best song in the competition's history as part of the 50th anniversary celebration of the contest.
https://en.wikipedia.org/wiki/ABBA