Historical clue formulations

• Archives material — 2017-02-12
• Piece of microfilm — 2011-11-28
• Archives unit — 2006-01-29
• Library holding — 2004-03-11
• Information storage unit — 2002-08-10
• Library microfilm — 2001-02-26
• Library material — 1999-08-22
• Micro add-on — 1995-11-21