Alberti, G., Ciofaniello, L., Galiero, G., Persico, R., Sacchettino, M., Signore, G.M. and Vetrella, S. 2003. Experimental results from a stepped frequency GPR. Annals of Geophysics. 46, 4 (Dec. 2003), 707–717. DOI:https://doi.org/10.4401/ag-4368.