1. Kast, W., Z. Physik, 71, 39 (1931). Freedericksz, V., and Zolina, V., Trans. Farad. Soc., 29, 919 (1933). Zwetkoff, V., Acta Physicochimica URSS, 6, 865 (1937).
2. Gray, G. W., Molecular Structure and the Properties of Liquid Crystals (a photograph of the threads is shown in Plate 3) (Academic Press, New York, 1962).
3. Maier, W., and Saupe, A., Z. Naturforschung, 14, a, 882 (1959).