References
The following references were available on the Internet at the time this was written (June 2012).
- Hurricane/Tornado Fire Safety (FEMA)
- Enhanced Fujita Scale for tornadoes — Wikipedia
- Disaster-Resistant Concrete Shell (Houses) — Concrete International
- List of F5 and EF5 tornadoes — Wikipedia
- Design and Construction of Low-Cost Disaster-Resistant Replacement Houses, ICF Builder magazine
- Four Inch Concrete Walls, ICF Builder magazine