They have dubbed them Bonnie and Clyde and are offering a $10,000 reward for tips leading to their arrests.
Authorities say the man robbed a Sinclair gas station on Dec. 5 and the pair robbed a cash advance store and a bank later in the month.
In each of the robberies, employees were threatened with guns.
If you have any information about the couple, you're asked to call the FBI or Greeley Police.
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