. 2009 Feb 24;50(1):60–67. doi: 10.3349/ymj.2009.50.1.60
Copyright © 2009 The Yonsei University College of Medicine
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited.