¹Yeats, William Butler. The Collected Poems of William Butler Yeats. London: Macmillan, 1955. 38.
The poem may be read in its entirety here.

²"Rostellan Portal Tomb" Megalithic Monuments Of Ireland. Web. 14 Dec. 2011. <http://www.megalithicmonumentsofireland.com/COUNTIES/CORK/Rostellan_PortalTomb.html>.
Due to its unusual orientation, and also due to its being repaired by Dr. Wise in the middle of the nineteenth century, some have suggested that the dolmen may be a fake, of entirely of modern construction. Others have described it as resembling a kist, rather than a portal tomb. An article in The Irish Naturalist following the account of the exploration of the Rostellan Dolmen describes a similarly submerged specimen near Etel, Morbihan, in NW France. ("A Parallel to the Submerged Cromleac of Rostellan, Co. Cork." The Irish Naturalist 19.3 (1910): 49.)

³Killanin, Michael Morris, and Michael V. Duignan. The Shell Guide to Ireland. London: Ebury P. in Association with George Rainbird, 1967. 166.
According to this online forum, Mhaistin may also derive from "Mastiff," or "unruly child," or "large ugly thing." Some claim that the name Rostellan comes from Ros (headland) and dallan or dolmen.

⁴"Rostellan Castle/House | Housetorian." Housetorian | The Story behind the House. Web. 15 Dec. 2011. <http://gatecottages.wordpress.com/2011/04/05/rostellan-castlehouse/.
The 5th Earl of Inchiquin Murrough O'Brien named the tower in honor of actress Sarah Siddons who apparently visited the Rostellan House. She was a British actress, a tall figure with "expressive eyes and a solemn dignity."

⁵The Rostellan Dolmen History 4 June 2010. Information sign at the site. Saleen.
The sign indicates that the stones on the shore are a themselves a megalithic tomb. Others believe them to be a quarry from which the dolmen's stones originated.

⁶Borlase, William Copeland. The Dolmens of Ireland... Vol. 1. London: Chapman & Hall, Ld., 1897. 16.
This volume may be read in its entirety here.

⁷Welch, R. "Further Note on the Rostellan Cromleac." The Irish Naturalist 16.9 (1907): 267-69.
The Dr. Wise mentioned in the article was a Scotsman who lived in Rostellan House from 1855-1879. According to the author, there was a Mrs. W. H. Johnson in the party of explorers "who stated that she had visited the cromleac some years previously, and that there was then a portion of a stone circle (three stones, which have since disappeared), and she was then informed that the circle was complete within the memory of persons then living."

⁸O'Sullivan, Sean. The Folklore of Ireland. London: B.T. Batsford, 1974. 30.

⁹"A Folklore Survey of County Clare: Rocks, Caves and Stones." Clare County Library. Web. 15 Dec. 2011. <http://www.clarelibrary.ie/eolas/coclare/folklore/folklore_survey/chapter18.htm>.
Some have suggested that the origin of the Diarmuid and Gráinne tale's connection to portal tombs may be the linguistic confusion arising from the word leabaidh, which was understood in its literal sense of a "bed," whereas it was intended to convey the sense of a "tomb."

¹⁰Cross, Tom Peete, and Clark Harris Slover. Ancient Irish Tales. New York: Barnes & Noble, 1936. 374.
"The Pursuit of Diarmuid and Gráinne" as translated in Ancient Irish Tales may be read in its entirety here.
Gráinne's name may come from that of the sun goddess, Grian. Diarmuid's full name is usually given as "Diarmuid Ua Duibhne," but some credit an ancient source for his alternate name of Diarmaid Donn, derived from Donn, the Celtic god of the dead. (Ó hÓgáin Dáithí. Fionn Mac Cumhaill: Images of the Gaelic Hero. Dublin: Gill and Macmillan, 1988. 166-75.)
Some have suggested that "The Pursuit of Diarmuid and Gráinne" had some influence on the Tristan and Iseult legend. Although that story developed in France during the 12th century, it is set in Britain. There are also parallels to the story of Lancelot and Guinevere.

¹¹Grinsell, Leslie V. Folklore of Prehistoric Sites in Britain. London: Newton Abbot, 1976. 42-3.
Some wedge tombs are also associated with Diarmuid and Gráinne. According to DáithíÓ hÓgáin, "the implication of associating huge landmarks in stone with the Fianna is that they were able to construct them due to their enormous strength." (Ó hÓgáin Dáithí. Fionn Mac Cumhaill: Images of the Gaelic Hero. Dublin: Gill and Macmillan, 1988. 308.)

¹²Borlase Vol. 2. 845.
According to T.J. Westropp, "In Hely Dutton's time (possibly on the same account) some sense of indecency attached, and a girl refused to guide him to those of Ballyganner in 1808, till she was assured that he was a stranger and ignorant of the local beliefs John Windele in July 1855 notes of the Mount Callan Dolmen 'fruitfulness of progeny in that.' I learned of an indecent rite taking place about 1902 at a dolmen for the same purpose." (Westropp, Thomas J. "Prehistoric Remains (Forts and Dolmens) in Burren and Its South Western Border, Co. Clare: Part XII: North Western Part (Continued)." The Journal of the Royal Society of Antiquaries of Ireland Sixth 5.4 (1915): 267-68.)

¹³Grinsell 42-3.

¹⁴Evans, E. Estyn. Irish Folk Ways. New York: Devin-Adair, 1957. 283.

¹⁵Boland, Eavan. The Journey and Other Poems. Manchester: Carcanet, 1987. 322.
The poem "Listen. This is the noise of myth." may be read in its entirety (with annotations) here.
A short biography of Eavan Boland may be read here.