Wilson, D. and Stuart, J. 1875. Notices of Sculptured Rocks and Boulders recently observed in Ohio and Kentucky, United States of America, and of the Probable Origin of the Cup-Markings which occur on Stones there and in other Countries. Proceedings of the Society of Antiquaries of Scotland. 11, (Nov. 1875), 266–272. DOI:https://doi.org/10.9750/PSAS.011.266.272.