Books by O. T. Helgerson
Thinning young Douglas-fir wes
Thinning young Douglas-fir west of the Cacades for timber and wildlife
Adaptive FIR annual report
Nitrogen fixation by scotch br
Nitrogen fixation by scotch broom (Cytisus scoparius L.) and red alder (Alnus rubra Bong.) planted under precommercially thinned Douglas fir (Pseudotsuga menziesii (Mirb.) Franco)