1. Altair Engineering, available at the internet at web site: http://www.altair.com. Interred at May 2002.
2. BASF Corporation, available at the Internet at web site http://www.basf.com/index.html. Interred at May 2002.
3. British Standards, BS 6658:1985, Specification for protective helmets for vehicle users.
4. Burr ST, Vogel DG. Material model development for impact analysis of oriented polypropylene foam structure, DOW Automotive, SAE No. 2001-01-0310, 2001.
5. Chou CC, Zaho Y, Lim GG, Patel RN, Shahab SA, Patel PJ. Comparative analysis of different energy absorbing materials for interior head impact. SAE No. 950332, 1995.