Historical clue formulations

• West Berlin used to be one — 2018-06-09
• Vatican City, vis-à-vis Rome — 2014-09-28
• Vatican City vis-à-vis Rome — 2014-03-13
• Vatican City, to Rome, e.g. — 1998-04-28
• Surrounded territory — 1997-04-11
• Group within a group — 1995-07-09