	Paul Walsh's first work concerning Ulster was his edition of the diary of Tadhg Ó Cianáin, which was a journal of the Flight of the Earls. This edition was published in 1916. It was followed by "Genealogie Regum et Sanctorum Hiberniae" in 1918, a previously unpublished collection of genealogies of kings and saints by the Four Masters. Further such studies included "The Will and Family of Hugh O'Neill" (1919; published in book form in 1930); "The Life of Aodh Ruadh Ó Domhnaill" (1922); "The Book of O'Donell's Daughter" (1929); and "Colonel Myles O'Reilly, Sheriff of County Cavan, 1641" (1935). 1920 saw the publication of "Leabhar Chlainne Suibhne: An account of the Mac Sweeney Families in Ireland, with Pedigrees". The dedication was " Nollaig Ó Muraíle describes it as "an important, well thought-out book, a work which no-one working on Donegal history can afford to ignore" (#3). Unfinished at his death was his edition of "Beatha Aodh Ruadh Ó Domhnaill" by Lughaidh Ó Cléirigh. However, this led to a "series of meticulous and penetrating studies that were to shed a great deal of light on the story of Mícheál Ó Cléirigh and the Four Masters" (#4), all of which were published in the 1930s and are still invaluable.