29 C.F.R. § 510.21
(b) The Standard Industrial Classification (SIC) codes listed in appendix A and B herein are designated in accordance with the Standard Industrial Classification (SIC) Manual, 1987, published by the Executive Office of the President, Office of Management and Budget. This incorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies may be obtained from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161. Copies may be inspected at all federal depository libraries in the Commonwealth of Puerto Rico; at the district office of the Wage and Hour Division, U.S. Department of Labor, New San Juan Office Building, 159 Chardon St., room 102, Hato Rey, PR 00918; at the Commonwealth of Puerto Rico Department of Labor and Human Resources, Prudencio Rivera Building, Munoz Rivera Avenue 505, Mato Rey, PR 00918; or at the National Archives and Records Administration (NARA). For information on the availability of this material at NARA, call 202-741-6030, or go to: http://www.archives.gov/federal_register/code_of_federal_regulations/ibr_locations.html. Establishments are classified according to their primary activity. The classification structure classifies industries by:
(3) Four-digit industry code, according to the level of industrial detail which may be required.
Each operating establishment is assigned an industry code on the basis of its primary activity, which is determined by its principal product or group of products produced or distributed, or services rendered.
[55 FR 12120, Mar. 30, 1990; 55 FR 12778, Apr. 5, 1990, as amended at 69 FR 18803, Apr. 9, 2004]