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Northern Illinois University
College of Law
David C. Shapiro Memorial Law Library

Basic Legal Research

Overview of Secondary Legal Sources

Secondary sources provide commentary and background information on the law and can point you towards useful primary sources. However, they are not actual law.

Unlike primary legal sources, secondary sources are generally not binding on courts (for an exception see Restatements, below). You may cite secondary sources in a memorandum or article when you wish to provide the reader with a more in-depth explanation of a topic.

It is a good idea to begin your research with secondary sources, especially if you are researching a topic you do not know well. Since secondary sources use primary sources as the basis for their discussion, looking at the primary sources referenced in a secondary source (cases, statutes, regulations, etc.) will provide you with an excellent basis from which you can begin analyzing and applying the law in that area.

  • The best way to begin research in a secondary source is by looking at its index and/or table of contents.
    • Print secondary sources will almost always have an index and/or table of contents of some kind, whether it is for a single work such as a treatise or for a large set such as the American Law Reports.
    • Not all online materials currently have indices and tables of contents, but they are being added to more and more titles.
  • Once you have located a relevant section, be sure to read it in its entirety so you understand the context in which the material is being presented. Taking a few sentences of the material out of context can greatly alter its meaning. Always read the full text of the material before relying on the information or drawing any conclusions.

Using secondary sources can be somewhat complex due to the variety of secondary sources available and the fact that each is organized somewhat differently.

The rest of this page describes various types of secondary sources in both print/online and how to use them effectively.

Legal Dictionaries

Black's Law DictionaryLegal dictionaries are useful because the legal definition of a term will often differ from the non-legal definition of a term. During the research process, look up terms you encounter to verify that your interpretation of the word is correct.

  • The Law Library has several print legal dictionaries available. One of the most frequently used is Black's Law Dictionary, 10th ed. (copies on Reserve and located elsewhere in the library)
  • The major legal databases (Bloomberg, Lexis Advance, Westlaw) have online legal dictionaries (login required to access)
  • has a free online legal dictionary at
  • Words and Phrases is a useful source similar to a dictionary. It provides judicial definitions of legal and non-legal terms. Information is compiled from headnotes containing judicial definitions. It is useful for discovering if any court, or a specific court, has ever defined a term or phrase. The Law Library's print copy (KF 156 .W57) is no longer updated as of 2015, but an up-to-date online version is available on Westlaw.

Legal Encyclopedias

Cover of Illinois JurisprudenceLegal encyclopedias provide very general information on a large number of topics, and can be used as a finding tool for primary authority.

  • Because they are written by the publisher's editorial staff and not by experts in the field they are not a very persuasive secondary source.
  • Each main topic (also referred to as an article) can be very large, sometimes encompassing more than one printed volume. Each article is then divided into sections addressing subtopics within an article.
Tips for using encyclopedias:
  • Using the encyclopedia's index and/or table of contents (in print or online) can help you find the relevant articles and sub-sections for the term you are researching. 
  • It may be easiest to initially research in print (even if the print version is out of date) to understand how the encyclopedia is structured and terminology in use. Then move your search online.
  • Once you find a relevant section, it can be helpful to browse the sections before and after it for additional useful information.
General Encyclopedias:
  • American Jurisprudence 2d (Am. Jur. 2d) is published by West and provides citations to the most "noteworthy" decisions on a particular topic. The Law Library's print copy (KF 154 .A42, outside the library in the North Wing) is no longer updated but this title is available on both Westlaw and Lexis Advance.
  • Corpus Juris Secundum (C.J.S.) is also published by West and attempted to include every reported decision on a particular issue. The Law Library's print copy (KF 154 .C62, outside the library in the North Wing) is no longer updated but this title is available on Westlaw.
Illinois Encyclopedias:
  • Illinois Jurisprudence (Ill. Jur.) is published by LexisNexis and is more practice-oriented than Illinois Law and Practice. The Law Library continues to update this title in print (KFI 1265 .L38 1992, Illinois Collection). It is also available on Lexis Advance and in the Lexis Nexis Digital Library.
  • Illinois Law and Practice (I.L.P. or Ill. L. & Prac.) is published by West and covers all areas of Illinois law. The Law Library's print copy (KF 154 .C62, outside the library in the North Wing) is no longer updated but is available on Westlaw.
Correctly Citing Encyclopedia Articles & Sections:

When providing a Bluebook citation to an encyclopedia article, use the full article name (e.g., Searches and Seizures) followed by the section number and then the year of publication.

  • Do not use the section name in the citation. Section names can be repeated from article to article and are not unique enough to identify your material.

Example: 67A Am. Jur. 2d Sales § 940 (2003).

Additional examples are under Sample Bluebook Citations.

Legal Treatises

Treatise on the Law of TortsA treatise is a work that extensively covers one topic.

  • Treatises are useful because:
    • They comprehensively cover a subject
    • They cite useful primary and secondary sources
    • They provide useful tools such as indexes, tables of cases cited, appendices, forms (features vary by treatise)
  • Treatises are usually written by lawyers or law professors
  • Treatises in print vary in length from a single volume to sets of over twenty volumes

Many -- but not all -- treatises are regularly updated. It is important to determine the age of any treatise you are considering using, especially if you are looking for current information.

  • Some print treatises are issued in a binder format, called loose-leaf format, which allows easy updating of pages as the law changes
  • Others may have pocket parts or annual supplements
  • However, some are only updated when a new edition is published

Sometimes you need to identify the state of the law at an earlier time. In these instances older editions of a treatise can be very useful.

How to find treatises:

Treatises available in print at the Law Library can be found through the NIU online catalog.

  • If you are not sure of the exact title or subject for the treatise, a keyword search will probably be the most useful.

Treatises are also available online in Bloomberg Law, Lexis Advance, the Lexis Nexis Digital Library, and Westlaw. Other publishers such as Wolters Kluwer and BNA also offer treatises online.

  • Be aware that just because a treatise is online it may not be 100% up-to-date.
    • Some online versions of treatises are not updated continuously and may only be updated periodically (for example, annually).
    • Check the information provided by the online vendor to verify the treatise's currency and update schedule.
Tips for using treatises online:
  • Depending on the database you may be able to browse treatise titles by topic and/or search for a specific title.
  • Make use of indexes, tables of contents and other finding aids available in online treatises just as you would with a print treatise. Simply doing a full-text search of a treatise may provide you with too much irrelevant information.
  • If the online treatise does not have an index, looking at the print version of the treatise (even if the print version is out of date) may help you better understand how the work is organized and the terminology used within it.


The term "periodicals" encompasses several types of publications that discuss trends and developments in the law. There are 5 general forms of legal periodicals:

Cover of a specialty journal1. Law reviews and law journals:
  • These titles are generally published by law schools and other scholarly organizations.
  • Articles in these publications will provide the longest and most comprehensive coverage of a topic.
  • Law reviews often contain information about 'hot topics' before other types of publications address the issue.
  • Sometimes an entire issue of a law review will be devoted to a single issue (usually published in conjunction with a symposium held at the law school), but usually the articles will be on a variety of topics.
  • Attorneys, judges, law professors, or other professionals are the usual authors of law review articles. Law students may also write articles for law reviews; these articles will be identified as a Comment or Note.
2. Special interest periodicals:
  • These periodicals are similar to law reviews and law journals, but focus on a single subject area (e.g., Environmental Law Journal, Journal of Intellectual Property Law).

The following types of publications are more practice-oriented and provide current information of interest such as docket information, rule changes, and current court decisions.

3. Association journals:
  • Articles in these publications tend to be shorter and focused on a single, practice-related issue. Examples include the ABA Journal, the Journal of the American Bar Association.
4. Legal newspapers:
  • Legal newspapers can have a national (e.g., National Law Journal) or local (e.g., Chicago Daily Law Bulletin) focus. They can be published daily, weekly or at other intervals. Many are available online through Lexis Advance or Westlaw.
5. Newsletters:
  • Topical updates from specialized groups or organizations, such as the Animal Law newsletter from the Animal Law Section of the Illinois State Bar Association.

Finding Periodical Articles Online

HeinOnline contains a variety of legal periodicals but also contains many other types of resources, so a general search in Hein may bring up many non-periodical materials. To limit your search to articles, try searching within these specific collections:

Legal databases such as Bloomberg Law, Lexis Advance and Westlaw all contain legal periodicals. Usually these will be located within "Secondary Sources" in each database.

  • Except for Hein Online, many online services may not have the full text of older legal periodicals, especially those published before 1990. Always verify database coverage before attempting to pull up the full text of an article. 
  • Law review articles are often very long. Because of this, full-text searching may result in many irrelevant results. Using field searching (author, title, citation, journal title) and/or segment searching (if available) can help achieve more targeted results.

American Law Reports (ALRs)

American Law Reports (ALRs) contain articles, called "annotations,"* which provide in-depth information about the case law (and statutes when relevant) related to a particular topic across multiple jurisdictions (both state and federal).  (Note: the word "annotation" as used in the ALR is used in an entirely different sense from the "annotations" you will see in annotated, statutory codes.)

  • Annotations are written by attorneys practicing in the area at issue.
  • The annotations present the available law on topic without commentary or analysis.
  • The topic is often a current controversy where two or more jurisdictions have followed different rules on factually similar situations.
  • ALRs are useful because of their comprehensiveness and timeliness:
    • Each annotation tries to pull together all of the precedential case law and statutes (when applicable) on that particular issue
    • Annotations are often published before the topic is published in other secondary sources.

Remember that the ALR annotations are simply compilations of references and summaries of materials. You must still locate and read the full text of the referenced cases and statutes and draw your own conclusions about the materials. Do not rely solely on the summaries in the ALRs.

There are several "series" of ALRs. The best way to search them, both online and in print, is by using the index.

  • All ALR series are available in both Lexis Advance and Westlaw.
  • The following are available in print in the Law Library: 
  • ALR Index: KF 132.6 .A543 2008 [no longer updated in print at the Law Library as of 2015]
    • A.L.R.: KF 132 .A 48 [in Storage]
    • A.L.R.2d: KF 132 .A516 [in Storage]
    • A.L.R.3d: KF 132 .A53 [in Storage]
    • A.L.R.4th: KF 132 .A532
    • A.L.R.5th: KF 132 .A533
    • A.L.R.6th: KF 132 .A534 (through vol. 85)
    • A.L.R.7th: Note: not available in print at the Law Library, available in Westlaw or Lexis
  • A.L.R. Federal Quick Index: KF 105 .A547 [no longer updated in print at the Law Library as of 2013]
    • A.L.R. Fed.: KF 105 .A54 [in storage]
    • A.L.R. Fed. 2d: KF105 .A541 (through vol. 75) [in Storage]
    • A.L.R. Fed. 3d: Note: not available in print at the Law Library, available in Westlaw or Lexis


Restatements are published by the American Law Institute. The purpose behind their creation was to unify topics in common law such as Contracts, Torts, and Property on a national basis. Restatements are created and revised by groups of experts in a particular discipline.

  • Restatements are written as rules, followed by explanations or comments.
  • Restatements are ordinarily seen as persuasive authority. However, it is possible for a court to adopt a section of a Restatement and thus make it mandatory (binding) authority in that court.
  • Each Restatement is divided into topics and numbered sections. Each numbered section begins with a boldfaced rule followed by one or more comments.
  • In addition to the main volumes, there are numerous appendix volumes that contain case annotations applying the restatement sections.
  • Depending on the topic, there can be a First, Second and Third series of a Restatement.
    • Not all topics have three series.
    • Each detail addressed by a Restatement on a particular subject may not necessarily be covered in every series, so you may have to look within all series of a Restatement to find information on your topic.

Tips for using Restatements online:

  • When searching on Lexis and Westlaw, make sure of the specific restatement and series before starting your search.
  • You may be searching a combined database of all Restatements, so when you are viewing the document make sure you know what series it is from and that the document represents the most current version (or the version in which you are interested).

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