1. Bertelson, R.C, in Techniques of Chemistry, III, Brown, J.H., Ed., New York: Wiley, 1971.
2. Guglielmetti, R. Photochromism, Molecules and Systems, Duer, H. and Bouas-Laurent, H., Eds., Amsterdam: Elsevier, 1990, pp. 314, 855
3. Krongauz, V., ibid., p. 793
4. Chu, N.Y., ibid., p. 493.
5. Crano, J.E., Kwak, W.C., and Welch, C.N., Applied Photochromic Polymer Systems, McArdle, C.D., Ed., London: Blackie, 1992, p. 31