1. Sleight RB, Cook KC, Problems in Occupational Safety and Health: A Critical Review of Select Worker Physical and Psychological Factors. HEW Publication (NIOSH) 75–124, US Government Printing Office, Washington, DC 1974 p A-4.
2. Brown JR: Manual: Lifting and Related Fields: An annotated bibliography, Ontario Ministry of Labor, Ontario, Canada 1972 p 16.