References
- U.S. Department of Labor, Occupational Safety and Health Administration . June 1989 . OSHA Instruction CPL 2.45B. The Revised Field Operations Manual June , Washington, DC : USDOL/OSHA .
- U.S. Department of Labor, Occupational Safety and Health Administration . 1992 . Construction Standard. Title 29, Code of Federal Regulations, Part 1926 Washington, DC : U.S. Government Printing Office .
- National Institute for Occupational Safety and Health . September 1985 . Safety and Health in Confined Workspaces for the Construction Industry, Training Resource Manual September , Cincinnati, OH : NIOSH .