Historical clue formulations

• Like some signs — 2025-03-26
• ___ signs — 2025-02-14
• Critical — 2021-07-18
• Life-sustaining — 2021-04-30
• Like some very important signs — 2018-02-17
• Essential — 2018-01-26
• Key — 2014-08-28
• Life-sustaining — 2012-03-26
• Life-or-death — 2010-10-05
• Key — 2009-03-06
• Key — 2008-04-04
• Essential — 2007-08-23
• Indispensable — 2005-02-15
• Critical — 2004-12-06
• Like some signs and statistics — 2004-10-15
• Like some organs — 2003-12-09
• Like some organs — 2000-12-02
• Critically important — 1999-08-02
• Like some statistics — 1999-04-16
• Essential — 1995-10-18
• Indispensable — 1995-02-12