Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2011 Jan 10;8(1):10.1371/annotation/0ef47acd-9dcc-4296-a897-872d182cde57. doi: 10.1371/annotation/0ef47acd-9dcc-4296-a897-872d182cde57

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

Public Library of Science. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PMC Copyright notice

graphic file with name pmed.0ef47acd-9dcc-4296-a897-872d182cde57.g001.jpg