Each printed volume in the series is a collection of selected documents deemed to be the most important or those that help to tell the story of the subjects covered. Until 2002 (series I, v. 1-7 ; series II, v. 1-4 ; and, series III, v. 1-3) were accompanied by microfiches in folders entitled: Microfiches of documents calendared in Documents on British policy overseas. The documents on the microfiches were summarized and listed in the accompanying printed volumes; which also refer to other material available in the Public Records Office and cite the relevant PRO file numbers.