10O'Kelly, M.J., Claire O'Kelly, V.R. O'Sullivan, and R.H. Frith. "The Tumulus of Dowth, County Meath." Proceedings of the Royal Irish Academy 83C (1983): 136-41.
Michael Herity has noted, "Passage Graves, probably because they often commanded a good view, seem to have been fairly often chosen as the sites of follies. Professor Ruaidhri de Valera has pointed out to me that the circular structure at the top of Clermont cairn in Co. Louth is probably the remains of one." (Herity, Michael. "From Lhuyd to Coffey: New Information from Unpublished Descriptions of the Boyne Valley Tombs." Studia Hibernica 7 (1967): 142, note 24.)