Abba was an Internationally successful Swedish pop group, active from 1972 until 1983, comprising vocalists Agnetha Fältskog and Anni-Frid Lyngstad; Björn Ulvaeus (guitars & vocals) and Benny Andersson (keyboards & vocals). The most commercially successful artists of the 1970s, their biggest hits include Dancing Queen, Fernando, Waterloo, Chiquitita, Mamma Mia, and Take A Chance On Me. Although sales figures for the group are widely varying, the official estimate is at 370 million records. Their music has seen a resurgence in interest in part due to the release of their multi-platinum greatest hits album “ABBA Gold” in 1992 and a general revival in interest in disco and ’70s music around the same time. Their music gained even greater visibility with the jukebox musical “Mamma Mia!” based on their hits, which opened in 1999 and is still running in venues around the world. ABBA were inducted into the Rock & Roll Hall of Fame in 2010 in the category of performer.