^Charles Haliday, ed. John Patrick Prendergast, The Scandinavian Kingdom of Dublin, Dublin: Thom, 1882, repr. Shannon, Irish University Press, 1969, ISBN0-7165-0052-3; see Allen, pp. 58-60 and notes 203, 204, p. 93 (calling him Halliday). The theory was first published by John O'Donovan in 1860, prior to the posthumous publication of Haliday's papers.
^Annals of Ulster, AU 845.8; Barbara E. Crawford, Scandinavian Scotland, Leicester University Press, 1987, ISBN0-7185-1197-2, p. 49, describes this as "the only historical fact that can be relied upon".