Franklin et al. (1981)

Franklin, J.F., Cromack, K. Jr., Denison, W., McKee, A., Maser, C., Sedell, J., Swanson, F., Juday, G. 1981. Ecological characteristics of old-growth Douglas-fir forests. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Gen. Tech. Rep. PNW-118.