Historical clue formulations

• Mooers' mouthfuls — 2017-04-02
• Things to chew on — 2016-12-04
• Cows chew them — 2006-08-28
• They're chewed in the field — 2005-03-31
• Things to chew on — 2000-03-26
• Cows' mouthfuls — 1998-12-15