NFPA 52-2013
http://www.nfpa.org/

SAE J2343-2009
http://www.sae.org/

California Administrative Code Title. 13, § 935 (13 CCR § 935)
http://www.oal.ca.gov/ccr.htm

Barclays Official California Code Of Regulations
      Title. 13 Motor Vehicles
            Division 2. Department of the California Highway Patrol
                 Chapter 4. Special Equipment
                       Article 2. Compressed and Liquefied Gas Fuel Systems (Refs & Annos)
                             935. Liquefied Natural Gas.