(CNN) Two men have pleaded guilty to theft and receiving stolen property charges after an alleged $8 million worth of rare books, plates and maps were taken from a Pittsburgh library and sold to a rare book store owner, court documents show.

The theft is among the world's largest losses to date, according to court documents.

Gregory Priore, a former archivist at the Carnegie Library of Pittsburgh, was originally charged with 10 counts but pleaded down to theft of unlawful taking and receiving stolen property. Both counts are felonies in Pennsylvania.

John Schulman, the owner of Caliban Book shop, originally received 20 charges but pleaded guilty to a forgery charge in addition to theft by deception and receiving stolen property.

In a statement provided to CNN, Schulman's attorney, Albert Veverka, said his client was "accepting responsibility for his association with books under circumstances whereby he should have known that the books had probably been stolen."

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