Revision of the call numbers assigned to selected items to make their relationship to other items in the collection more consistent, for example, to reflect the merger of two classes very similar in subject. Also refers to the conversion of a collection (or part of a collection) originally cataloged under one classification system to another, for example, from Dewey Decimal Classification (DDC) to Library of Congress Classification (LCC), or vice versa. Also refers to the removal of previously declassified government documents from public access. American Libraries reported in its March 2006 issue that U.S. Archivist Allen Weinstein called upon all intelligence and security agencies on March 2, 2006 to cease removing documents from the open shelves of the National Archives and Records Administration (NARA) and to return as many records as possible which they pulled as part of a secret program in operation since 1999. His call for the moratorium was prompted by a letter from a group of historians who complained that the CIA, the Defense Department, and the Department of Justice had withdrawn approximately 9,500 documents from the Korean War and Cold War periods for purposes of reclassification.