1. T. M. Maitland, unpublished work (2005).
2. Figures 2.2–2.4, assistance of Robert Schwarzer is gratefully acknowledged.
3. K. Shinohara, Sci. Pap. Inst. Phys. Chem. Res., 20 (1932/1933) 39.
4. Boersch Physikalische Zeitschrift, 38 (1937) 1, 000.
5. M. N. Alam, M. Blackman, and D. W. Pashley, Proc. Roy. Soc., 221(1954) 224.