1. Riberholt H, Madsen PH (1979) Strength of timber structures, measured variation of the cross sectional strength of structural lumber. Report R 114, Structural Research Laboratory, Technical University of Denmark
2. Schniewind AP, Lyon DE (1971) Tensile strength of redwood dimension lumber II. Prediction of strength values. Forest Prod J 21:45–55
3. Johansson CJ, Brundin J, Gruber R (1992) Stress grading of Swedish and German timber. A comparison of machine stress grading and three visual grading systems. Swedish National Testing and Research Institute, SP Report 1998:38
4. Machado JS, Sardinha RA, Crus HP (2007) Feasibility of automatic detection of knots in maritime pine timber by acousto-ultrasonic scanning. Wood Sci Technol 38:277–284
5. Baradit E, Aedo R, Correa J (2006) Knots detection in wood using microwaves. Wood Sci Technol 40:118–123