Historical clue formulations

• – — 2019-09-22
• – — 2019-05-31
• Hyphen's longer cousin — 2018-04-22
• Hyphen's longer cousin — 2017-07-24
• - — 2014-06-15
• Mark slightly longer than a hyphen — 2009-08-17
• Long hyphen — 2009-02-19
• Minus sign equivalent — 2007-10-06