1. S. M. Aldoshin, L. O. Atovmyan, O. A. D’yachenko, and M. A. Gal’bershtam, Molecular and crystal structure of l,3,3-trimethyl-6′-nitro-8′-bromospiro(indoline-2,2′-[2H-l[benzopyran) and the product of its photochemical transformation, Izv. Akad. Nauk SSSR, Ser. Khim. 1981, 2720–2729.
2. P. Shibaeva, L. P. Rozenberg, A. S. Kholmanskii, and A. V. Zubkov, Crystalline and molecular structure of photochromic spiropyrane,C 24 N 2 O 3 H 20 Dokl, Akad. Nauk SSSR 226,1374–1377 (1976).
3. R. P. Shibaeva and R. M. Lobkovskaya, On crystal and molecular structure of a photochromic spiropyran,C 24 N 2 H 19 CL,Zh. Strukt. Khim. 20, 369–373 (1979).
4. Sh. Karaev, N. G. Furmanova, and N. V. Belov, On crystal and molecular structure of a photochromic spiropyran,C 19 H 18 N 2 O 3 , Dokl. Akad. Nauk SSSR 262, 877–880 (1982).
5. S. M. Aldoshin and L. O. Atovmyan, Structure of the new photochromic spiropyran of indoline series C 19 H 18 N 2 O 3 , Izv. Akad. Nauk SSSR, Ser. Khim. 1985, 191–194.