³⁶Waddell, John, Joe Fenwick, and K. J. Barton. Rathcroghan: Archaeological and Geophysical Survey in a Ritual Landscape. Dublin: Wordwell, 2009. 77.
The author reports, "The earthwork was subjected to detailed topographical survey and a suite of geophysical techniques, including magnetic susceptibility, fluxgate gradiometry, twin-probe electrical resistance and electrical resistivity tomography surveys. The geophysical survey has identified a number of interesting anomalies that are undoubtedly of archaeological significance. These anomalies, for the most part, have no visible surface expression and were unknown prior to the present study." (66)