Application of ground penetrating radar (GPR) to delineate clay layers in wetlands. A case study in the Soto Grande and Soto Chico watercourses, Donana (SW Spain) - Gomez-Ortiz, D.; Martin-Crespo, T.; Martin-Velazquez, S.; Martinez-Pagan, P.; Higueras, H.; Manzano, M.; (Journal Of Applied Geophysics, 2010)