Historical clue formulations

• Nat and Natalie — 2007-08-14
• Duo that had a hit with "Unforgettable" — 2006-07-22
• "Unforgettable" singers — 2005-02-11
• Nat and Natalie — 2004-02-29
• Nat and Natalie — 2003-10-20
• "Unforgettable" singers — 1997-12-18
• Composer Porter and others — 1996-06-04
• Father-and-daughter singers — 1996-04-13
• Nat and Natalie — 1995-03-27