Historical clue formulations

• River to the Ubangi — 2015-08-11
• Congolese river — 2011-02-27
• River to the Ubangi — 2010-05-25
• One of two rivers forming the Ubangi — 2006-08-27
• River to the Ubangi — 2003-07-24
• Congo river — 2000-04-27
• River to the Ubangi — 1999-02-20
• Congo river — 1999-02-16
• Ubangi tributary — 1997-05-23
• River to the Ubangi — 1995-05-17
• River to the Ubangi — 1994-12-25