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The public domain includes works that are no longer in copyright or were never copyrightable. These works can be copied, distributed, or used for derivative works without restriction.
Works published by the US federal government are all in the public domain.
Works published in the United States before 1923 are now all in the public domain, as are some works published later if certain criteria were not met. Use the Digital Copyright Slider to determine if a work is in the public domain.
Some works are not copyrighted, for example works where the copyright has expired, or works by the federal government. However, the rules of attribution, meaning citing the sources of information used in your own work, still apply. Even when using out of copyright works, it is important to properly cite the sources you've used. Failure to do so is a violation of Plymouth State University's Academic Integrity Policy.