1. Dinwoodie, J. M. 1963. Variation in tracheid length in Picea sitchensis (Carr.), Spec. Rep. For. Prod. Res., No. 16, London.
2. Drow, J. T. 1957. Relationship of locality and rate of growth to density and strength of Douglas-fir. U.S. Forest Service, Forest Prod. Lab. Rept. 2078, 56pp.
3. Duffield, J. W. 1964. Tracheid length variation patterns in Douglas-fir and selection of extreme variants. TAPPI 47 (2): 122?124
4. Erickson, H. D., Lambert, G. M. G. 1958. Effects of fertilization and thinning on chemical composition, growth, and specific gravity of young Douglas-fir. For. Science 4: 307?315.
5. Gerry, E. 1916. Fiber measurements studies. A comparison of tracheid dimensions in longleaf pine and Douglas-fir with data on the strength and length, mean diameter and thickness of wall of tracheids. Science 43: 360.