1. Balls, W. L., "Studies of Quality in Cotton" (London: Macmillan, 1928), Figs. 3–9.
2. Goshawk, E. R., unpublished, summarized in W. L. Balls (ref. 1)
3. Slater, F. P., Proc. Roy. Soc., B, 96, 121 (1924). (Summary in W. L. Balls, ref. 1.)
4. Balls, W. L., Nature, 152, 389 (1943).