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The assistant to a presidential historian has pleaded guilty, saying they were both responsible for conspiring to steal historical documents.

Jason Savedoff, 24, said he and historian Barry H. Landau worked together to steal various historical items, The Associated Press reported.

The documents include papers signed by Abraham Lincoln valued at about $300,000, CNN reported.

Savedoff faces up to 12 years in prison, The AP reported. Media outlets have reported that the young man was polite during court proceedings.

Landau is the author of The President's Table: Two Hundred Years of Dining and Diplomacy. His Web site is filled with photos of him with political figures, media members and other high-profile people. He is awaiting trial, CNN reported.

He's disappointed that Jason Savedoff appears to be shifting his illegal acts toward Barry, said Landau's lawyer, Steve Silverman, The AP reported. He felt very close to Jason Savedoff at one time. Barry is a very sensitive person and this is very hurtful.