J. R. Allen, “Report on the Sculptured Stones older than A.D. 1100, with Symbols and Celtic Ornament, in the District of Scotland, North of the River Dee; obtained under the Victoria Jubilee Gift of His Excellency Dr. R. H. Gunning, F.S.A. Scot”, PSAS, vol. 25, pp. 422–431, Nov. 1891.