Secondary Sources

A good place to start most research projects is with a secondary source. A secondary source is not the law. It's a commentary on the law. A secondary source can be used for three different purposes: it might educate you about the law, it might direct you to the primary law, or it might serve as persuasive authority. Few sources do all three jobs well. The important classes of legal secondary sources include: treatises, periodical articles, legal encyclopedias, ALR Annotations, Restatements, and Looseleaf services. This guide will provide a brief description of these sources, please also visit our secondary sources tutorial and our finding articles tutorial for more information.


In this context, legal treatises are single or multi-volume works dedicated to the examination of an area of law. Treatises tend to be very good at describing the law, they're good law finders, and many of the classic treatises are persuasive. Treatises tend to provide an in-depth discussion of a particular area of law and will provide the researcher with references to a few cases and statutes.   The Legal Information Buyer’s Guide and Reference Manual describes the important legal treatises in several areas of the law. To identify and locate a legal treatise, use a library catalog like MORRIS (searching by topic and handbook, or topic and nutshell) or the Georgetown Treatise Finder. Note that the word treatise is not often associated with a legal treatise in the catalog record.

Legal periodicals

Legal periodical articles are in-depth discussions of narrow areas of the law and legal issues. Articles in academic journals tend to revolve around very theoretical and cutting-edge legal issues. Articles in practitioner-oriented journals tend to be more practical. Periodical articles can be very good law finders; they tend to have a great many footnotes with a lot of legal citations. Some articles by eminent scholars can be persuasive. Occasionally, legal periodical articles can be useful for explaining the law, but often they are too theoretical for that. The major American legal periodical indexes are the Index to Legal Periodicals (also on Lexis and Westlaw) and LegalTrac. In addition to the two major North American periodical indexes described above, there are many indexes devoted to articles on particular topics. When using an index database such as a legal periodical index or a library catalog, a good strategy is to identify a book or article that looks relevant, notice the subjects or descriptors assigned to the item by the indexer or cataloger and run a new search based on the subjects or descriptors found. In general, full-text sources are not very good tools to use for finding periodical articles on a particular topic. However, there are several databases that include full-text legal periodical articles; Lexis and Westlaw contain the full text of articles from many law reviews from roughly the past decade. Hein Online contains the full text of legal periodical articles for many hundred law reviews from their inception until a year or two ago. To use a full-text tool to find periodical articles, a user has to construct an online search and the online search will return articles that contain the particular language that the user chose. An index, on the other hand, will get a user articles that an editor has decided are about the topic selected.

Legal encyclopedias

Legal encyclopedias are immense sets of books that briefly describe all of the main legal issues for a particular jurisdiction. An encyclopedia can provide a basic introduction to an area of law and will provide the user with some case and statutory citations. Legal encyclopedias will not delve deeply into an area, nor will they discuss the finer points of an area of law. Legal encyclopedias are available online and in print. The two national encyclopedias are American Jurisprudence and Corpus Juris Secundum. Many states also have legal encyclopedias, which are available in print or online (Lexis/Westlaw).


ALR provides topical annotations that focus on relatively narrow areas of the law, but discuss it in some depth. They provide a good basic grounding in law, as well as serve as good case finding tools. ALR is available in print and on Lexis and Westlaw. Annotations can be identified in print by using the ALR Index to Annotations and online via online searches. Please note that the ALR titles tend to be very descriptive. So it can be useful to limit your search to the title field. In addition, the second section of an ALR annotation generally covers related annotations. This is the often worth examining.


The restatements were developed by legal scholars initially to restate the law, and currently to describe what the law should be. In either case, Restatements are very persuasive although they are not very good at describing the law. They can serve as adequate law finders. There are restatements for many areas of law: but not all. The Restatements are available on Lexis and Westlaw and in print. Online, they can be searched in full-text; in print you would use the library catalog to identify the relevant restatement and then the restatement’s own index to find the relevant sections.

Looseleaf Services

Looseleaf services bring together all of the law on a particular topic. Looseleaf services don't exist for all areas of law, but when they do exist, they can be an invaluable resource. They are rarely cited except when they serve as a case reporter. However, for a researcher, they bring together in one place the code, administrative regulations, court decisions, administrative decisions, citators, finding aids, commentaries, forms, etc. Looseleaf services are moving online. To identify a relevant Looseleaf service, whether in print or online, use the Legal Looseleafs in Print or a directory search in Lexis/Westlaw.

Common Secondary Sources (with descriptions):