| 1 | Notebooks and early career |
| 1.1 | School and College work |
| 1.2 | Notebooks |
| 1.3 | Early career |
| 2 | General correspondence |
| 3 | Publications and drafts |
| 3.1 | Publications |
| 3.1.1 | Books |
| 3.1.1.1 | "Historical Studies" vol.4 1963 |
| 3.1.1.2 | "The Irish at war" 1965 |
| 3.1.1.3 | "Ulster and other Irish maps, c.1600" 1964 |
| 3.1.1.4 | "Irish battles" 1969 |
| 3.1.1.5 | "A history of Irish flags from earliest times" 1979 |
| 3.1.2 | Scholarly articles |
| 3.1.3. | Press |
| 3.1.4. | Drafts for scholarly articles |
| 3.2 | Lectures, radio and television work |
| 3.2.1. | Public lectures |
| 3.2.2. | Radio and television work |
| 3.2.2.1 | Book reviews 1955 |
| 3.2.2.2 | Thomas Davis Lecture series (Raidió Eireann) 1 1955-1963 |
| 3.2.2.3 | "Irish battles" (Teilifís Eireann) 1965 |
| 3.2.2.4 | "The long winter" (Raidió/ Teilifís Eireann) 1965-1966 |
| 3.2.2.5 | Thomas Davis Lecture series (Raidió Eireann) 2 1966-1971 |
| 4 | Foundation of the Military History Society of Ireland 1949 and editorship of "The Irish Sword" |
| 4.1 | The Military History Society of Ireland |
| 4.2 | "The Irish Sword" |
| 5 | Other academic work and related interests |
| 5.1 | Participation at conference, delegations |
| 5.2 | Collaboration over Dublin pageants |
| 5.2.1. | Military Tattoo and Exhibition 1945 |
| 5.2.2 | "Trumpet call" 1953 |
| 5.2.3. | An Tóstal "Pageant of St.Patrick" 1954 and 1955 |
| 5.2.4. | An Tóstal "Pageant of Cú Chulainn" 1956 |
| 5.3 | Galway interest |
| 5.3.1 | General, and lecturing aids |
| 5.3.2 | Lion's Tower campaign |
| 5.4 | Involvement with The Bureau of Military History |
| 6 | Private interest: drawings and exhibitions |
| 6.1 | Drawings |
| 6.2 | Exhibitions |
| 7 | Collected material |
| 7.1 | Historical sources and copies: general |
| 7.2 | Material on Galway |
| 7.3 | Other printed material |