The first official publication of a federal statute is as a "slip law." For an explanation of the federal process, see the Library of Congress - Congress.gov Website. The Office of the Federal Register prepares the federal slip laws, and assigns a law number (they are sequentially numbered, starting with each new Congress), a legal statutory citation and publishes them individually in an unbound pamphlet. The pamphlet also includes the date of approval and bill number.
Slip laws also include marginal notes from the Office of the Federal Register. Some of the information included: the United States Code citation, the popular name of the law, and a guide to the legislative history of the law with a reference to the Congressional Record by volume, year, and date.
Copies of slip laws are held in the Document Offices of both Houses, where they are available to the public. Physical copies are available for purchase from the Superintendent of Documents and free electronic copies are available on the GPO FDsys website. Copies may also be available in Federal Depository Libraries.
At the end of a congressional session, the slip laws will be compiled, indexed and published in bound volumes - the Statutes at Large.
At the end of a congressional session, the slip laws from that Congress are compiled, in chronological order, into bound volumes called the United States Statutes at Large, and referred to as session laws. The Statutes at Large is the official source, published by the GPO under the guidance of the Office of the Federal Register, for the laws and resolutions passed by Congress.
There is also an unofficial source of the federal session laws published by West, the United States Code Congressional & Administrative News (U.S.C.C.A.N.). U.S.C.C.A.N. is published monthly in soft cover pamphlets, and cumulated in a bound volume at the end of the year.