Ground penetrating radar (G.P.R.) surveys applied to the research of crypts in San Sebastiano's church in Catania (Sicily)http://www.sciencedirect.com/science/article/pii/S1296207406001142GPRhttp://www.subsurfacesurveys.com/gpr.htmhttp://www.ees.nmt.edu/outside/courses/Geop446/Docs/GPR_survey_design.pdfSinkhole detection in Florida using GPR and CPThttp://www.dot.state.fl.us/statematerialsoffice/geotechnical/conference/materials/bullock-dillman.pdf Resolution and Energy Penetrationhttp://mysite.du.edu/~lconyers/SERDP/variablesaffecting2.htm