Picture taken in 1974 in Stockholm shows the Swedish pop group Abba with its members (L-R) Benny Andersson, Anni-Frid Lyngstad, Agnetha Faltskog and Bjorn Ulvaeus posing after winning the Swedish branch of the Eurovision Song Contest with their song "Waterloo". – Sweden's legendary disco group ABBA announced on April 27, 2018 that they have reunited to record two new songs, 35 years after their last single. The quartet split up in 1982 after dominating the disco scene for more than a decade with hits like "Waterloo", "Dancing Queen", "Mamma Mia" and "Super Trouper". (Photo by Olle LINDEBORG / TT News Agency / AFP) / Sweden OUT (Photo credit should read OLLE LINDEBORG/AFP via Getty Images)
(L-R) Swedish singers Benny Andersson, Anni-Frid Lyngstad, Agnetha Fältskog and Björn Ulvaeus, of the Swedish supergroup ABBA, pose for a portrait at Polar Studios in Stockholm, Sweden, May 1981. (Photo by Oscar Abolafia/TPLP/Getty Images)
Swedish pop group Abba, wearing kimonos, 1976. Left to right: Bjorn Ulvaeus, Agnetha Faltskog, Frida Lyngstad and Benny Andersson. (Photo by RB/Redferns/Getty Images)
(L-R) Technician Michael Tretow sits behind the audio mixer sound board with Swedish musicians Björn Ulvaeus and Benny Andersson, of the supergroup ABBA, at their Polar Studios in Stockholm, Sweden, circa 1977. (Photo by Oscar Abolafia/TPLP/Getty Images)
