Statutes at Large are the official source of laws and resolutions passed by Congress.
At the end of each session of Congress, the slip laws are compiled into bound volumes called the Statutes at Large, and they are known as "session laws." The Statutes at Large present a chronological arrangement of the laws in the exact order that they have been enacted.
http://www.gpo.gov/help/index.html#about_public_and_private_laws.htm
