U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH),
NIOSH HETA No. 2006-0155-3072: 1-40
International Telecommunication Union (ITU),
Directives concerning the protection of telecommunication lines against harmful effects from electric power and electrified railway lines: 1-74, ISBN 978-92-61-12501-1