The "SUDOC" classification system is an alphanumeric design based on the principle of "provenance", or issuing agency, whereby the publications of any government entity are grouped under like notation. It is not a subject classification scheme like the Library of Congress or Dewey decimal system.
Because the system is based on the current organizational status of an agency, it changes with government reorganization, and over a period of time, publications of some issuing agencies will be located in many places within the document collection. When doing historical research keep in mind that some current departments grew out of others and therefore older materials may well be shelved under a different number.
A complete SUDOC classification notation consists of three major elements: an author symbol, a series designation representing the type of document, and a book accession number. The combination of author symbol and series designation, typically found before the colon, is called the "class stem". The book number gives the publication its unique identification and completes the notation.
For example: I 29.9/5: 139
I = Department of the Interior (author symbol)
29 = National Park Service (secondary author symbol)
.9/5 = Handbooks (series designation)
139 = Document number (the unique id #)
When you are searching for a document in the govdocs collection, there is one thing you must remember: the Sudoc system is NOT a decimal system--the " . " is not a decimal point--therefore the number after the " . " is a WHOLE number. For comparison:
Decimal Order:
D 1.1
D 1.12
D 1.122
D 1.3
D 1.33
SuDoc Order:
D 1.1
D 1.3
D 1.12
D 1.33
D 1.122