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2. The Photochemistry and Photophysics of Spiropyrans
3. R. Guglielmetti, in: Eds. H. Dürr, H. Bouas-Laurent, Studies in Organic Chemistry, Vol. 40, Photochromism — Molecules and Systems (Elsevier, Amsterdam, 1990) p. 314.
4. Photo- and thermochromic transients from substituted 1',3',3'-trimethylindolinobenzospiropyrans