. 2012 Nov 23;7(1):644. doi: 10.1186/1556-276X-7-644
Copyright ©2012 Chen et al.; licensee Springer.
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.