The Library of Congress guide for Researching Judicial Decisions provides a good introduction and overview of resources to consult when researching judicial decisions (court opinions). Many free online sites provide access to federal decisions. For more comprehensive searching use LexisNexis Academic or Westlaw Next below.
Secondary sources explain and provide context for understanding the law. They also provide references to statutes and cases and are often the best way to begin your legal research.
Legal Encyclopedias
Legal encyclopedias offer broad and general commentary on a full range of federal and state law. They are useful as a starting point for researching unfamiliar areas of law. Most articles in encyclopedias focus on case law and do not contain extensive citations to statutes or other secondary sources. They are a good source for finding a brief review and some of the key terminology that can help you create better online keyword searches. Legal encyclopedias are not intended to be authoritative sources of the law
American Jurisprudence 2d is available in LexisNexis Academic: Search by Subject or Topic > Legal > Legal Reference > Advanced Options. Am Jur 2d articles summarize broad principles of law and provide citations to cases and statutes.
American Law Reports is available in Westlaw Next: Home > All Content > Secondary Sources. ALR provides in-depth articles on narrow topics of law. Includes background, analysis and citations.
Law Journals
Law journals publish articles with comprehensive studies of current topics in law. Articles are generally written by practitioners and academics, and contain citations to primary and secondary sources on the topic providing leads to additional relevant information.
In LexisNexis Academic: Search by Subject or Topic > Law Reviews
In Westlaw Next: Home > All Content > Secondary Sources to find.
Case citations are used to refer to opinions and identify where they have been published in reporters.
Elements of a citation include:
Example: United States v. Pepperman, 976 F.2d 123 (3d Cir. 1992).
The citation above identifies a decision in a case between the plaintiff, United States, and the defendant, Pepperman. The decision was published in volume 976 of the Federal Supplement, Second Series (F.2d), beginning on page 123. The citation shows the opinion was issued by the United States Third Circuit Court of Appeals in 1992.
The Bluebook: A Uniform System of Citation provides rules governing the most widely used legal citation formats. A useful introduction to legal citation is Peter W. Martin, Introduction to Basic Legal Citation (2016).
Official Case Reporters for Federal Cases
Abbreviations for all reporters may be searched in LexisNexis Academic: Search by Subject or Topic > Shepare's Citations > Citation Formats. See also, Common Legal Abbreviations.
Short Form Citations
Once a full citation to a case has been provided, subsequent references may use a shortened form. The most common short form generally includes the name of first nongovernmental party along with volume and reporter abbreviation.
Example of long and short form citations from Cornell:
Full Citation: Brown v. Helvering, 291 U.S. 193, 203 (1934).
Short Form:
According to the Bluebook, once a full citation has been provided a short citation may be used if the following conditions are met:
For additional guidance see Cornell University Library guides:
Use the following tools to verify that a case is still considered "good law," i.e., it has not been overturned on appeal, questioned, or received other negative treatment
If you have a citation, retrieve the case from Lexis-Nexis Academic 
or Westlaw Next
If you do not have a citation, use a secondary source such as a legal encyclopedia to get an overview of the subject and references to relevant primary sources such as case, regulations and statutes.
REPORTERS
Most New York court decisions can be retrieved from Lexis-Nexis Academic, Westlaw Next, the courts, and other case law sites on the web such as Findlaw. The Libraries have the following print reporters.
New York Reports, Reports of Cases Argued and Determined in the Court of Appeals of the State of New York, 1st and 2d (Library Annex)
Official reporter of NYS cases. Library owns through 2002. See Lexis-Nexis Academic, Westlaw Next or court web sites for subsequent decisions.
New York Supplement, 1st and 2d KFN 5045 .A33-A333 (3rd floor)
A commercial publication, with annotations, reporting decisions for cases argued in New York State courts (Court of Appeals, Appellate Division of the Supreme Court, Supreme Court, and others). Library owns through 2007. See Lexis-Nexis Academic, Westlaw Next or court web sites for subsequent decisions.
New York Miscellaneous Reports KFN 5051 .A5
The library owns v.1-208, 1892-1955. (Library Annex)
New York Court of Appeals Reports KFN 5045 .A18
The library owns v.1-309, 1859-1955. (Library Annex)
N. Y. Supreme Court, Appellate Division Reports KFN 5048 .A22
Appellate Division Reports (Library Annex)
The library owns series 1, v.1-286, 1896-1955.
DIGESTS
Abbott New York Digest 2d 1930-1961 KFN 5057 .A2 1971 (3rd floor)
West's New York Digest 3d 1961-1978 KFN 5057 .A2 1979 (3rd floor)
West's New York Digest 4th 1978-present REF KFN 5057 .A2 1989
Digests contain brief excerpts of case facts or court opinions and are classified by subject. Because case reporters are published chronologically, digests are often necessary to locate opinions relevant to a particular topic. Digests may be used to find the citation to cases when only a subject area or certain facts of the case are known.
Digests serve as indexes to New York State court cases. There is an index to cases by plaintiff and defendant, and a word index to the subject headings used in the main body of the index.
Chapter or Session Laws: A New York State bill passed into law is referred to as a "chapter law," or a "session law". Published chronologically in McKinney's Session Laws of New York, Ref K .N57 .A4 A. Also includes memoranda commenting on individual statutes, the governor's messages, and the like. Kept up-to-date by paperbound supplements. Library holds 1952-present.
There are two types of published law:
New York Code Rules & Regulations (NYCRR) (unofficial version)
Official Compilation, Codes, Regulations of the State of New York (Ref KFN5025 .A3) Official version with current rules and regulations of all state agencies. Arranged by issuing agency in looseleaf.
Also available from :