U.S. Statutes at Large. Law review articles, treatises, legal encyclopedias, digests, and looseleaf reporters are secondary sources. Unofficial sources are commercially published and often more timely. They are editorially enhanced to improve usefulness as a research tool. Annotations can include case summaries, citations to cases interpreting the law, referrals to relevant periodical articles, legislative history, editorial notes, and analysis.
Unannotated sources publish the bare text of the law.