In this and the other pages of this gallery the sources of maps, diagrams and photographic images have been referenced on that particular illustration. The Kentucky Geological Survey is a source of most of the measured sections for Route 23, while many of the maps and diagrams tracking continental paleogeography were created by Dr. Ron Blakey of Northern Arizona University at Flagstaff, Arizona; while the paleogeographic maps and cross sections for the late Paleozoic of the Appalachians were created by Dr. Lynn S. Fichter of the Department of Geology/Environmental Science of James Madison University in Harrisonburg, Virginia. Most of the photographs are by Christopher Kendall using a digital Nicon Coolpix camera, and a number were taken by Dave Barbeau.