Historical clue formulations

• Streaked — 2013-01-25
• Make furrows in — 2010-02-24
• Having grooves — 2008-07-13
• Make furrows in — 2006-11-12
• Streaked — 2003-05-11
• Furrowed — 2000-04-08
• Groovy — 1994-02-05