National Safety Council. (1956). Supervisors safety manual; better production without injury and waste from accidents. s.n.
Lua i Stíl Chicago (17ú heag.)National Safety Council. Supervisors Safety Manual; Better Production Without Injury and Waste from Accidents. Chicago: s.n, 1956.
Lua MLA (9ú heag.)National Safety Council. Supervisors Safety Manual; Better Production Without Injury and Waste from Accidents. s.n, 1956.
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