Safety rules for radio installations :
comprising part 5 of the 5th ed., National Electrical Safety Code.

APA Citation

United States. National Bureau of Standards. (1939). Safety rules for radio installations: comprising part 5 of the 5th ed., National Electrical Safety Code. Washington: U.S. Govt. Print. Off.

MLA Citation

United States. National Bureau of Standards. Safety Rules for Radio Installations: Comprising Part 5 of the 5th Ed., National Electrical Safety Code. Washington: U.S. Govt. Print. Off, 1939.

Warning: These citations may not always be complete (especially for serials).