Keating, Narrative of an Expedition to the Sources of the St Peter (Minnesota) River, Lake Winnepeek, Lake of the Woods, &c....
Keating, History of the City of Memphis and Shelby County, Tennessee (Syracuse, 1888); James Phelan, History of Tennessee (Boston, 1889).
They are also embodied in the Leabhar Gabhala or Book of Invasions, the earliest copy of which is contained in the Book of Leinster, a 12th-century MS., Geoffrey Keating's History, Dugald MacFirbis's Genealogies and various collections of annals such as those by the Four Masters.
These stories naturally become amplified as times goes on, and in what we may regard as the classical or standard versions to be found in Keating, the Four Masters, Dugald MacFirbis and elsewhere, no fewer than five successive invasions are enumerated.
Many authorities such as Keating and MacFirbis admit that descendants of the Firbolgs were still to be found in parts of Ireland in their own day, though they are characterized as " tattling, guileful, tale-bearing, noisy, contemptible, mean, wretched, unsteady, harsh and inhospitable."