1. ChargeSearch, Llano, Texas, USA..
2. The University of Texas at Austin, Institute for Geophysics, Austin, Texas, USA..
3. The University of Texas at Austin, Institute for Geophysics, Austin, Texas, USA; The University of Texas at Austin, Department of Petroleum and Geosystems Engineering, Austin, Texas, USA; and The University of Texas at Austin, Bureau of Economic Geology, University Station, Austin, Texas, USA..