Historical clue formulations

• Mailers: Abbr. — 2011-06-08
• Ltr. holders — 2008-10-12
• Ltr. carriers — 2007-12-09
• Stationery store stock: Abbr. — 2007-04-28
• Ltr. holders — 2004-02-17
• Stationery store stock: Abbr. — 2000-08-19