Annotated codes are very useful because they describe a statute's history, list and describe case's that interpret a statute, provide citations to relevant regulations, and also provide references to other sources, such as ALR annotations, treatises, law reviews, etc. Usually this material appears immediately after the text of the statute. By using an annotated code rather than an official code, a researcher finds a wealth of information interpreting that statute, simply by retrieving a relevant section.
Federal statutes appear in two unofficial annotated codes, the United States Code Annotated, published by Thomson West, and the United States Code Service, published by LexisNexis.
New York annotated codes currently appear in two versions, McKinney's Consolidated Laws of New York Annotated, published by Thomson West, and New York Consolidated Law Service, published by LexisNexis.