Young & Company Electric Power Products and Related Engineering Services, Glossary of Electrical Terms, http://www.youngco.com/young2.asp?ID=4&Type=3, CA., USA 2001. (Electr Sfty - Amer) {514}
Ralph W. Burklin & Robert G. Purington, Fire Terms: A Guide to Their Meaning and Use, National Protection Association, Boston, MA 1980 USA. (Guide: Meaning and Use, Nat Prot Association Fr Srvc - Amer) {457}