Version history for



  Spudich, Paul, Chiou, Brian S.J., Graves, Robert, 
       Collins, Nancy, and Somerville, Paul, 2004, A 
       formulation of directivity for earthquake sources 
       using isochrone theory:  U.S. Geological Survey 
       Open-File Report 2004-1268 [available on the World 
       Wide Web at http://pubs.usgs.gov/of/2004/1268/].


  Version 1.0

  July 29, 2004
  Added a legal notice to the acknowledgments section

  July 20, 2004
  Intital release online at
  http://pubs.usgs.gov/of/2004/1268/