1. Childe V. G. , Skara Brae: A Pictish Village in Orkney (1931), pls. LIII, LIV. Piggott, op. cit., fig. 33 11a, 12a.
2. Piggott S. , Neolithic Cultures of the British Isles (1954), figs. 13. 62.
3. Royal Commission on Historical Monuments, A Matter of Time (1960), fig. 6, 69.