Federal government documents are organized by the Superintendent of Documents (SuDoc) classification scheme, not by the Library of Congress call numbers used in the rest of the library. The University of Texas at El Paso has created a fantastic SuDoc classification tutorial:
The Superintendent of Documents (SuDoc) classification system classifies each document by an institutional author (Congress or a government department or agency), rather than by subject. In other words, it is organized by who created the document.
The following example for SuDoc number I 29.9/5: 125 illustrates this system.
|I||=||Department (Department of the Interior)|
|29||=||Agency (National Parks)|
|9||=||Type of publication (type of document, e.g. an annual report, newsletter, bibliography, etc.)|
|5||=||More information about the type of publication|
A SuDoc number is a call number assigned to a government publication. SuDoc is an abbreviation for Superintendent of Documents.