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Guide to Interpreting SuDoc Classification Numbers

Tips for locating US Government Publications shelved using the Superintendent of Documents Classification System

Basic Shelving Rules

1. Periods, back slashes, and colons separate each section of a SuDoc Number.  Documents are shelved alphabetically by the letters and then numerically, section by section.

C 1.1:

C 1.2:

C 1.24:

C 2.1:


2. All numbers are shelved as whole numbers, not decimals.

              HE 20.40

              HE 20.108:

              HE 20.3016:


3. Single letters are shelved before multiple letters. Multiple letters are shelved alphabetically, regardless of the number of letters.

              L 2.3: 

              LC 4.7:

              N 11.5:

              NAS 1.21:

              NS 1.2:    

Complete Shelving Rules

The Government Publishing Office provides a complete explanation of the Superintendent of Documents Classification System.