Historical clue formulations

• Hard things to carry alone — 2021-03-12
• What best friends keep — 2013-07-14
• Exchange of spies, maybe — 2010-01-03
• Spies seek them — 2008-06-04
• Bad things to share — 2008-06-01
• Spies seek them — 2002-12-31
• Fraternity handshakes, maybe — 2000-01-16
• What tellers lack? — 1999-12-16
• Spies' quest — 1999-11-13
• 1985 Danielle Steel best seller — 1994-06-07