Government agencies publish material on a wide variety of subjects. Materials using this classification system are grouped together according to the agency that produced them, rather than by subject. This means that items concerning unrelated subjects may be located on the shelf next to each other, as long as they were produced by the same agency.
SuDocs call numbers consist of two parts: Agency number : book number
The agency number identifies the agency that created/generated the document and begin with letters of the alphabet. One or more numbers following the letter(s) represents a division of the primary agency.