Secondary sources are material that help explain, summarize, or analyze law. They provide helpful context and citations to the primary law relevant to your topic. This page provides information on the most commonly-used types of secondary sources. Also see this guide from Lexis Advance for assistance in using the platform's secondary sources:
A treatise is a scholarly legal publication focusing on the law relating to a particular area. They are often made up of multiple volumes and provide in-depth commentary and analysis on that subject. Treatises are often known by the name of the original author, even if that person is no longer responsible for its content (e.g. Wigmore on Evidence or Corbin on Contracts). You should consult a treatise when you are looking for an in-depth discussion of an area of law or the answer to a specific question. Treatises are available in print in the Reserve Reading Room, as well as online in Lexis Advance, Westlaw, and other legal research platforms. For a list of the major treatises by subject, consult the D’Angelo Law Library Treatises page.
Legal encyclopedias are just what they sound like—encyclopedias that focus on law and law-related issues. They provide a general overview rather than in-depth critical analysis and include footnotes to statutes, case law, and other primary authority on the topics covered. You should consult a legal encyclopedia when you are new to a particular area of law or topic.
Most of the larger states also have at least one legal encyclopedia focused on that state’s law. For example, for Illinois, there are two legal encyclopedias:
For other states, check the secondary sources available within Westlaw or Lexis Advance:
ALRs analyze specific legal topics in essays called “annotations”. They often summarize differences among jurisdictions, providing citations to cases addressing the same issue in the different states or circuits. There are ALRs for both state and federal law. Not every legal issue has an annotation, but if one exists, a relevant annotation can provide a great starting point for research. ALR annotations are especially helpful when you want to know how different jurisdictions have treated a legal issue. ALRs are available online in both Lexis Advance and Westlaw:
Law journals, or law reviews, are journals that include well-researched articles that typically provide in-depth analysis of a narrow issue of law. They contain extensive footnotes that point you to relevant primary authority and other secondary sources. Since they tend to focus on a narrow issue of law, law journal articles are generally not the best place to begin your research, unless you are working on a particularly specialized or cutting edge topic. Lexis Advance and Westlaw both contain databases of articles of most U.S. law reviews articles, although the coverage generally begins around 1980. For older articles, or to access articles in PDF format, consult the online database HeinOnline: