Historical clue formulations

• Trees used in furniture-making — 2019-12-29
• Some desk materials — 2014-10-11
• Trees in the mint family — 2010-09-11
• Trees of the verbena family — 2009-01-31
• Durable woods — 2007-02-09
• Furniture woods — 2006-06-07
• Trees used in shipbuilding — 2005-04-25
• Ship woods — 2003-09-05
• Shipbuilders' woods — 2002-12-10
• Shipbuilding woods — 1999-02-08