4Dowth, Brú na Bóinne. 2 June 2010. Information sign at the site. Dowth.
The "Stone of the Seven Suns" is considered in the context of its "ancient astronomical symbolism" here. Other sources for discussions of the rock art at Dowth include:
Coffey, George. "On Stone Markings (Ship-Figure) Recently Discovered at Dowth, in the County of Meath." Proceedings of the Royal Irish Academy 4 (1889-1901): 586-88.
Coffey, George. "On the Tumuli and Inscribed Stones at New Grange, Dowth, and Knowth." The Transactions of the Royal Irish Academy 30 (1892/1896): 51-67.
O'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): 158-59.