Historical clue formulations

• "This statement is false," e.g. — 2023-04-18
• "Less is more," for one — 2022-08-12
• Logical conundrum — 2022-05-08
• Logical contradiction ... or an aural hint to what are found in 20-, 25- and 45-Across — 2021-02-24
• Potential consequence of time travel — 2019-05-03
• What 3- and 9-Down are an example of — 2014-05-08
• "This statement is false," e.g. — 2014-04-25
• Catch-22 — 2006-05-25
• Puzzle — 2002-09-06
• Piers 19 and 20? — 1994-02-16