1. Formerly Bullard Laboratories, University of Cambridge, Department of Earth Sciences, Madingly Road, Cambridge CB3 0EZ, United Kingdom; presently Universidad Central de Venezuela, Department of Applied Physics, Caracas, Venezuela..
2. Bullard Laboratories, University of Cambridge, Department of Earth Sciences, Madingly Road, Cambridge CB3 0EZ, United Kingdom..
3. Laboratoire de Geosciences Marines, Institut de Physique du Globe, 4 Place Jussieu, 75252 Paris, Cedex 05, France. .
4. Formerly Bullard Laboratories, University of Cambridge, Department of Earth Sciences, Madingly Road, Cambridge CB3 0EZ, United Kingdom; presently University of Durham, Department of Earth Sciences, Durham DH1 3LE, United Kingdom..