This package is "United States Government Work" under the terms of the United States Copyright Act. It was written as part of the authors' official duties for the United States Government and thus cannot be copyrighted. This software is freely available to the public for use without a copyright notice. Restrictions cannot be placed on its present or future use. Although all reasonable efforts have been taken to ensure the accuracy and reliability of the software and data, the National Human Genome Research Institute (NHGRI) and the U.S. Government does not and cannot warrant the performance or results that may be obtained by using this software or data. NHGRI and the U.S. Government disclaims all warranties as to performance, merchantability or fitness for any particular purpose. In any work or product derived from this material, proper attribution of the authors as the source of the software or data should be made, using "NHGRI Genome Technology Branch" as the citation.