Stone Monuments.
Simms, S. C. American Anthropologist, vol. 5, n. s., pp. 107 and 374. 1903.
Swastika.
Wilson, T. Report of the United States National Museum, pp. 757 ff. A general discussion. 1894.
Brower, C. de W. Records of the Past, 1907, pp. 236 ff. 1907.
Tablets.
Rau, C. Smithsonian Contributions to Knowledge, vol. XXII, p. 331. Palenque. 1879.
Campbell, J. American Antiquarian, vol. 4, p. 145. Davenport. 1882.
Brinton, D. G. The Archæologist, 1893, p. 201. Long Island. 1893.
Montgomery, H. American Anthropologist, vol. 8, p. 645. Dakota. 1906.