APA
American Petroleum Institute A., . (2011). Contractor safety performance process. Washington: American Petroleum Institute, API.
Chicago
American Petroleum Institute API, . 2011. Contractor safety performance process. Washington: American Petroleum Institute, API.
Harvard
American Petroleum Institute A., . (2011). Contractor safety performance process. Washington: American Petroleum Institute, API.
MLA
American Petroleum Institute API, . Contractor safety performance process. Washington: American Petroleum Institute, API. 2011.