. 2011 Apr 20;2:49. doi: 10.4103/2152-7806.79771
Copyright: © 2011 Amirjamshidi A.
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 author and source are credited.
Figure 1.
(a) Standard helmet. (b-d) Nonstandard helmets