Historical clue formulations

• Artificial — 2022-11-29
• Like Lake Mead — 2016-06-22
• Like Lake Mead or Lake Powell — 2015-02-15
• Artificial — 2014-04-18
• Unnatural — 2011-09-04
• Not natural — 2010-11-15
• Like Lake Mead — 2001-04-28
• Synthetic — 1995-10-08
• Artificial — 1994-08-19
• Unnatural — 1994-03-05