The Library of Congress Classification System is used in most large public and university libraries today. A Library of Congress (LC) number has three lines: a letter at the top, a number in the middle, and a letter/number combination at the bottom.

The Library of Congress went through several systems before devising its own method. Because the Library of Congress contains almost every book ever published in the United States, as well as valuable tapes and research materials, it requires a flexible system. The Library of Congress Classification System contains 20 classes:


A -- General works
B -- Philosophy, psychology, and religion
C-F -- History
G -- Geography, anthropology, recreation
H -- Social science
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 and library science


Cataloging In Publication Data

On the copyright page of most books, under the heading "Cataloging in Publication Data," are numbers and abbreviations that help librarians to index new acquisitions for the card catalog. These data can be helpful to readers as well. A typical entry is shown below with an explanation of each part of the entry:


Library of Congress Cataloging in Publication Data
McLanathan, Richard B.K.
World art in American museums.
[Possible subject card headings, in order of importance]
1. Art -- United States -- Guide-books. 2. Art museums -- United States -- Guide-books. 5. Art -- museums -- Guide-books. 6. Museums -- Canada -- Guide-books.
[Library of Congress No.]
1. Title
N510.M34 1983 708.13 (Dewey Decimal No.)
ISBN 0-385-18515-4 (International Standard Book Number: country number; publisher number; title number; and check digit. The ISBN was started by the British in 1967 and adopted in the United States a year later.)


Cataloging in Publication Data might also include information on a book's illustrator, whether a book has an index or bibliography, and number of pages.