This is the official version of the U.S. Code. It is published by the Government Printing Office (GPO), which produces a completely revised edition once every six years. In the interim, the U.S. Code is updated by an annual cumulative supplement. However, the annual supplement may be up to two years out of date. Consequently, while The Bluebook prefers an author to cite to the official version of the U.S. Code for briefs and scholarly writing, few attorneys use it to do research.