APA (7th ed.) Citation

Curtis, R. O. (2013). True fir spacing and yield trials: 20-year update. United States Department of Agriculture, Forest Service, Pacific Northwest Research Station.

Chicago Style (17th ed.) Citation

Curtis, Robert O. True Fir Spacing and Yield Trials: 20-year Update. Portland, OR: United States Department of Agriculture, Forest Service, Pacific Northwest Research Station, 2013.

MLA (9th ed.) Citation

Curtis, Robert O. True Fir Spacing and Yield Trials: 20-year Update. United States Department of Agriculture, Forest Service, Pacific Northwest Research Station, 2013.