Both the main sources of archive material and the attitude of historians to archives have evolved over the period in question. The major source of official records was for a long time the Public Record Office (PRO), founded in 1838, whilst private papers were surveyed and published by the Historical Manuscripts Commission (HMC, 1869). These merged in 2003 to form The National Archives (TNA). As the professional discipline of history emerged in the late 19th century it was still felt by many that there was no need to study original documents if a transcript or summary was available in print, but the idea of historical research being grounded in archival research (usually at the PRO) soon developed. A similar shift (with regard to the work of the HMC) occurred from the 1950s on as historians increasing obtained access to sources in local and specialist repositories rather than having to rely on the published surveys of the HMC. Developments in IT have also changed both the methods with which archives can be interrogated and the contents of the archives themselves, as increasing records are stored in digital form.