Historical clue formulations

• Abbr. at the bottom of a page of text — 2017-12-21
• More to come: Abbr. — 2015-03-31
• End-of-page abbr. — 2009-10-03
• Afr. or Eur. — 2006-10-04
• Abbr. at the bottom of a page — 2003-05-02
• N.A., e.g. — 1999-01-01
• Serial abbr. — 1998-04-07