. 2012 Oct 30;7:147. doi: 10.1186/1746-1596-7-147
Copyright ©2012 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.