Biographies, the written histories about a person's life, are also cataloged and shelved a little differently. To keep all the biographies about a person shelved together, a Cutter number is assigned for the biographee. For example, all the biographies about George W. Bush are shelved by the call number 973.931 B62.
A second cutter number is assigned for the author of the biography. For example:
Dowd, Maureen. Bushworld: Enter at Your Own Risk