Historical clue formulations

• Property of curium, but not cerium — 2026-01-25
• Committee head? — 2023-05-28
• Head of cabbage? — 2021-01-09
• The fourth letter of "circle," but not the first — 2019-06-24
• Can opener? — 2018-08-31
• Corporate head? — 2011-11-08
• What's in carrots but not celery? — 2011-03-16
• Head of cattle? — 2010-12-24
• Croc's head or tail? — 2006-10-25
• Leader of Congress? — 2005-04-17
• It starts and ends seven answers in this puzzle — 2002-12-12
• Capital of Colombia? — 2002-10-23
• Third letter of recommendation? — 2002-03-24