Manuscripts
Manuscript:
Dublin, Royal Irish Academy, MS 23 F 16 = O'Gara manuscript
  • 1655-1659
Ó Macháin, Pádraig, “‘One glimpse of Ireland’: the manuscript of Fr. Nicolás (Fearghal Dubh) Ó Gadhra, OSA”, in: Gillespie, Raymond, and Ruairí Ó hUiginn (eds.), Irish Europe, 1600-1650: writing and learning, Irish in Europe 5, Dublin: Four Courts Press, 2013. 135–162.  
abstract:
A description and analysis of the Irish manuscript known as The Book of O'Gara (RIA MS 2 (23 F 16)), written in Lille and Brussels, 1655-9, by an Irish Augustinian, Fr Nicolás (Fearghal Dubh) Ó Gadhra. The paper also gives an account of the manuscript's history subsequent to its return to Ireland, particularly the addition to it of an address to the reader, composed, it is suggested, by Seaán Ó Gadhra.
(source: http://rian.ie)
“Royal Irish Academy”, Ó Macháin, Pádraig (director), Irish Script on Screen – Meamrám Páipéar Ríomhaire, Online: School of Celtic Studies, Dublin Institute for Advanced Studies. URL: <https://www.isos.dias.ie/libraries/RIA/english/index.html>.
“MS 23 F 16 (The Book of O'Gara)”
Walsh, Paul, “Farewell to Inis Fáil”, in: Walsh, Paul, Gleanings from Irish manuscripts, 2nd ed. (1918), Dublin: Three Candles, 1933. 3–11.
Internet Archive: <link>