NASA's Thermal Infrared Multispectral Scanner (TIMS) detects over 200 miles of a precolumbian (900 CE or 1000 CE) road system in Chaco Canyon, as well as walls, buildings and agricultural fields.[4]
O'Kelly, Michael J.; O'Kelly, Claire (6 April 1989). Early Ireland: An Introduction to Irish Prehistory. Cambridge University Press. p.xi. ISBN9780521336871.