References
- Turnbull , John M. 1937 . Variations in Strength of Pine Timbers . South African Journal of Science , Vol. xxxiii March : 653 – 682 .
- Markwardt , L. J. and Wilson , T. R. C. 1935 . Strength and Related Properties of Woods Grown in the United States , United States Department of Agriculture . Technical Bulletin No. 479, Sept.