1. Pediatric injuries in the back of pickup trucks;Agran;JAMA,1990
2. Statistical abstract of the United States, 1988;Bureau of the Census,1988
3. 1990 census of population and housing. Summary tape files 1A, 1C, and 3A;Bureau of the Census,1992
4. State of California Vehicle Code. Sacramento, CA: Department of Motor Vehicles, 1991.
5. Californians' view on driving: A survey of the attitudes and opinions of California's motoring public;The Field Institute,1991