1. Alexander, R. R., 1987: Ecology, silviculture, and management of the Engelmann spruce—subalpine fir type in the central and southern Rocky Mountains. USDA Forest Service. Ag. Handbook No. 659. Washington, D. C.
2. USDA Forest Service Ge. Tech. Rep. RM;R. R. Alexander,1984
3. Gen. Techn. Rep. PNW-GTR-219;W. A. Farr,1988
4. Farr, W. A.;Harris, A. S., 1979: Site index of Sitka spruce along the Pacific coast related to latitude and temperatures. For. Sci.25, 145–153.
5. USDA Forest Service Gen. Techn. Rep. NE-5;R. M. Frank,1973