1. M. Milligan A. Burl (1999), Circles of Stone, London.
2. M. Hoskin (1997), The Cambridge Illustrated History of Astronomy, Cambridge.
3. Milligan Burl, op. cit.
4. Annals of the Four Masters“, see Vistas Astron. 41, 117 (1997).
5. P.A. Wayman (1987), Dunsink Observatory, 1785–1985 - A Bicentennial History, Dublin.