Historical clue formulations

• Imperatives — 2025-04-22
• Nonnegotiables — 2024-11-17
• They're mandatory — 2023-11-23
• Imperatives — 2016-02-04
• They're required — 2006-09-12
• Imperatives — 2003-08-05
• Indispensables — 1997-01-26
• Obligations — 1995-06-09