| "How did they pass the Union?" : Secret Service expenditure in Ireland 1799-1804 | Wilkinson, David | Article in Journal | | 1997 |
| Castlereagh | Bartlett, Christopher John | Monograph or Collective Volume | Macmillan | 1966 |
| Castlereagh | Hinde, W. | Monograph or Collective Volume | | 1981 |
| Castlereagh | Derry, John W. | Monograph or Collective Volume | Allen Lane | 1976 |
| Castlereagh : a biography | Leigh, Ione | Monograph or Collective Volume | Collins | 1951 |
| Castlereagh : from enlightenment to tyranny | Bew, John | Monograph or Collective Volume | Quercus | 2011 |
| Castlereagh : the biography of a statesman | Bew, John | Monograph or Collective Volume | Quervus | 2014 |
| Castlereagh and the making of the Union | Geoghegan, Patrick M. | Article in Book | | 2001 |
| Castlereagh, Captain Hamilton and General Cockburn : an ancient Greek (?) tombstone in County Down | Whitehead, David | Article in Journal | | 1995 |
| County Down elections, 1783-1831 | Jupp, Peter, 1940-2006 | Article in Journal | | 1972 |
| Lord Castlereagh | Hughes, Philip | Article in Journal | | 1937 |
| Lord Castlereagh | Geoghegan, Patrick M. | Monograph or Collective Volume | Dundalgan Press for the Historical Association of Ireland | 2002 |
| Lord Castlereagh : the rediscovery of a statesman | Bartlett, Christopher John | Monograph or Collective Volume | | 1969 |
| Memoirs and correspondence of Viscount Castlereagh | | Monograph or Collective Volume | [s.n.] | 1848 |
| Some British reactions to the Irish Act of Union | Bolton, G. C. (Geoffrey Curgenven) | Article in Journal | | 1965 |
| The death of Lord Londonderry | Franklin, Robert | Article in Journal | | 2007 |
| The parentage of Colonel Robert Stewart of Irry, Co. Tyrone | King, R. G. S. | Article in Journal | | 1941 |
| The parliamentary background of the Irish Act of Union of 1800 | Bolton, G. C. (Geoffrey Curgenven) | Thesis | | |
| The rise of Castlereagh | Hyde, Harford Montgomery | Monograph or Collective Volume | | 1933 |
| The support of Connacht's Catholic hierarchy for the Legislative Union of Great Britain and Ireland, 1800 | Hogan, Patrick | Article in Journal | | 2006 |
| William Vitruvius Morrison's Scheme for Mount Stewart County Down : was it ever realised? | Casement, Anne | Article in Journal | | 2004 |