Bluebook 101

The basic citation form for federal statutes, as they appear in the official reporter, appears below:

The U.S. Code or "U.S.C." is the official reporter for U.S. federal code. 

The same code sections appear in the U.S. Code Annotated (U.S.C.A) and the U.S. Code Service (U.S.C.S.).  However, neither the U.S.C.A (an annotated code produced by Westlaw) nor the U.S.C.S.(an annotated code produced by Lexis) are considered the official version of the U.S. Code.