UCD Digital LibraryGroup of IFS Army soldiers firing artillery on the Four Courts photograph, 28 June 1922
National Archives UK Cabinet Memorandum. Ireland – Capture of Four Courts. open_in_new document, 30 June 1922
National Museums IrelandThe last letter written by Seán Mac Diarmada (Sean MacDermott) letter, 11 May 1916
Bodleian Library blog 100 years ago: Constitutional Crisis and the Parliament Act of 1911 open_in_new article, 2011