1. Preparative Organic Synthesis [Russian translation], Inostr. Lit., Moscow (1956), Vol. 7, pp. 33?34.
2. J. Ritter, US Pat. 2,466,276; Chem. Abst.,43, 5038 (1949).
3. J. S. Davidson, J. Chem. Soc. C, No. 22, 2069 (1966).
4. L. V. Vilkov, V. S. Mastryukov, and N. I. Sadova, Determination of the Geometric Structure of Free Molecules [in Russian], Khimiya, Leningrad (1978), p. 224.
5. S. Baggio, L. N. Becka, L. M. Amzel, et al., Cryst. Struct. Commun., No. 2, 531 (1973).