Historical clue formulations

• Central support — 2026-09-13
• Book identifier, often — 2024-12-13
• It's attached to covers and sheets — 2024-11-10
• Courage — 2024-07-20
• Fortitude — 2024-03-31
• Fortitude — 2019-06-23
• Backbone — 2017-07-17
• Title locale — 2017-03-17
• Backbone — 2015-07-27
• Chiropractor's target — 2013-07-30
• Contortionist's bendy part — 2012-04-08
• Backbone — 2012-03-19
• Chicken's lack — 2011-01-22
• Moral fiber — 2009-10-02
• Title holder — 2009-03-07
• Subject for a chiropractor — 2007-08-15
• Coward's lack — 2007-08-08
• Place for a title — 2005-03-08
• It has disks — 2002-09-27
• Title holder? — 2002-01-02
• Porcupine's pointer — 2001-09-26
• Refusal to buckle — 2001-07-26
• Tingle area? — 2000-12-27
• Gumption — 1999-10-10
• Coward's lack — 1999-08-31
• Vertebra locale — 1997-01-27
• Quill — 1996-08-09
• Hardcover part — 1996-02-29
• Stiffness — 1994-12-31
• Part of a book — 1994-08-16