Historical clue formulations

• Volga tributary — 2012-01-06
• River to the Volga — 2009-05-02
• Volga feeder — 2008-11-20
• Volga feeder — 2007-03-04
• River to the Volga — 2005-09-13
• River in Irkutsk — 2005-06-04
• River to the Volga — 2002-10-13
• Russian river — 2002-10-10
• 900-plus-mile Volga feeder — 2001-12-28
• Volga feeder — 1996-03-22
• Volga tributary at Gorki — 1995-04-21
• Volga tributary — 1994-05-03