. 2010 Apr 6;3:93. doi: 10.1186/1756-0500-3-93
Copyright ©2010 Liu et al; licensee BioMed Central Ltd.
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.