Historical clue formulations

• "Careful!" — 2021-09-13
• "Watch it!" — 2021-01-22
• Advance warning — 2018-01-14
• Warning appropriate for this puzzle? — 2016-04-19
• "Fore!" — 2012-11-06
• "Look out!" — 2003-01-31
• Alert — 2001-07-28
• Alert — 1995-12-30