Standard industrial classification manual, 1972 :
1977 supplement.

APA Citation

United States. Office of Federal Statistical Policy and Standards. (1981). Standard industrial classification manual, 1972: 1977 supplement. [Washington, D.C.]: U.S. Dept. of Commerce, Office of Federal Statistical Policy and Standards .

MLA Citation

United States. Office of Federal Statistical Policy and Standards. Standard Industrial Classification Manual, 1972: 1977 Supplement. [Washington, D.C.]: U.S. Dept. of Commerce, Office of Federal Statistical Policy and Standards , 1981.