Historical clue formulations

• Doo-wop group with six songs on the "Grease" soundtrack — 2021-06-08
• Doo-wop rock band that performed in the movie "Grease" — 2020-02-03
• Group that appeared in the movie "Grease" — 2016-08-28
• Evoker of 1950s nostalgia — 2012-06-23
• Musical group with its own 1977-81 TV show — 2010-03-08
• Nostalgic 1970's variety show — 2006-11-12
• Next-to-last performers at the first Woodstock — 2006-06-29
• Bowzer's singing group — 2006-06-14
• Doo-wop group that sang in "Grease" — 2005-08-22
• Repeated part in "Get a Job" — 2002-03-23
• Woodstock band, 1969 — 2000-08-13
• Fifties revival group — 1999-12-12
• Woodstock group, 1969 — 1996-05-18
• '70s pop greasers — 1995-10-22