1. P. Grosberg. “The D.F.E. of Wool”-Leeds University Thesis 1952.
2. F. P. Bowden and D. Tabor. “The Friction and Lubrication of Solids”. Oxford U.P. 1950, 172- 173.
3. A. Love. “Mathematical Theory of Elasticity” Cambridge University Press, 159.
4. R. K. Makinson. Private Communication.
5. J. Sikorski. “Surface Properties of Animal Fibres”, Leeds University Thesis, 1948.