1. Mineral Sciences Department, Natural History Museum of Los Angeles County, 900 Exposition Boulevard, Los Angeles, California 90007, U.S.A.
2. Institute of Physics ASCR, v.v.i., Na Slovance 1999/2, 18221 Prague 8, Czech Republic
3. Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, Indiana 46556, U.S.A.
4. Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112, U.S.A.
5. 5199 East Silver Oak Road, Salt Lake City, Utah 84108, U.S.A.
6. U.S. Geological Survey (Ret.), Reston, Virginia 20190 U.S.A.