Research Guides: International Relations *: Library of Congress Classification System

Library of Congress Classification System

Although many research resources, including books, are available online, the USC Libraries still acquires and maintains a large collection of print materials. Most of these items are organized on unrestricted, open shelves according to a classification system developed by the United States Library of Congress.

This classification scheme ensures that materials are grouped together under the same subject categories, making it easier to locate related items by browsing the shelves next to the book you want. This does not mean, however, that ALL items on a topic will be in the same section. For example, books that examine a broad topic, such as "women in politics," might be located under women's studies, political science, history, sociology, communications, and many other disciplines, all of which are assigned call numbers corresponding to different areas of shelves in the library. This is why searching a topic in the Library Catalog may give you a list of items with completely different call numbers.

For more detail about how materials are arranged by subject area classification, click on the letter.

A -- General works
B -- Philosophy, psychology, religion
C -- Auxiliary sciences of history
D -- World history and history of Europe, Asia, Africa, Australia, New Zealand, etc.
E -- History of the Americas -- America and the United States
F -- History of the Americas -- United States local history, British America, Dutch America, French America, Latin America (Spanish America)
G -- Geography, anthropology, dance, recreation
H -- Social sciences
J -- Political science
K -- Law
L -- Education
M -- Music
N -- Fine arts
P -- Language and literature
Q -- Science
R -- Medicine
S -- Agriculture
T -- Technology
U -- Military science
V -- Naval science
Z -- Bibliography, library science, information resources (general)

How to Read Call Numbers

Call numbers are located on the spine or on the front of the book in the lower left-hand corner. The call number consists of a combination of letters and numbers that are read left-to-right, top-to-bottom. For example, if you searched the library catalog and wanted to check out a book from the Joseph Medicine Crow Center Library entitled, Defeating Dictators: Fighting Tyranny in Africa and Around the World by George B. N. Ayittey, the call number would be shown as JQ1879.A15 A98 2011.

In this example, you would read this call number in the following way in order to locate it on the shelf:

JQ	Read in alphabetical order: JQ is shelved after JN and before JS
1879	Read in numeric order as a whole number: 1879 is shelved before 1880 but after 1878
.A15	Read the letter in alphabetical order; read the number as a decimal: .A15 is shelved before .A151
A98	If there is another letter/number combination, read the letter alphabetically and read that number as a decimal even though the decimal point is omitted: A98 is shelved before A732
2011	If there's a publication date, read it in chronological order [this really only matters if there are multiple editions of the same book]

NOTE: Not every letter or combination of letters in the alphabet are used for identifying items on the shelf. In the above example, the next closest books on the shelf before JQ is JN. There are no books with call numbers beginning with the letters JO or JP. And, there are no books after JQ that are cataloged under JR. The next items on the shelf are call numbers beginning with JS. Reading call numbers can be confusing at first, but the more you search the shelves for items, the easier it gets.

ANOTHER NOTE: Besides the year of publication, there are other abbreviations you may encounter when reading a call number. This includes:

Copy Designation [e.g., c. 2] -- indicates the library owns more than one copy of the same book and this is the second copy.
Edition of the Book [e.g., 4th ed.] -- an identification of the edition does not necessarily indicate the library owns any or all of the previous editions.
Volume in a Series [e.g., vol. 12] -- this is used when there is a sequence of multiple items of the same title such as an encyclopedia.
Number in a Series [e.g. no. 4] -- stand-alone books published in successive parts that contribute research about a specific area of study or theme of analysis.
Part of a Set of Materials [e.g., pt. 3] -- used for a mixture of various materials issued as a unit, such as, a math curriculum workbook that includes a packet of activity cards and a teachers guide.
Supplement to Another Work [e.g., Suppl.] -- item intended to update or add additional content to a previously published work.

With the exception of needing a particular edition because its contents may be unique or have been changed or updated since the prior edition(s) were published, these abbreviations are rarely important in identifying where an item sits on the shelf. All numbered designations are arranged in sequential order; a supplement is always on the shelf next to the item it relates to.

YET ANOTHER NOTE: In some cases, you may come across a call number on the shelf, such as JC 423 .O93 2018, which in this case identifies the book, The Oxford Handbook of Deliberative Democracy. In this example, the O93 refers to the letter "O" and not the number zero. When looking for books on the shelf, note that the space between the first and second or the second and third line of a call number is always followed by the capital letter "O" and never the number zero.