1. I. E. Purvis, J. Chem. Soc., 103, 1638 (1913).
2. I. E. Purvis, Messeland, J. Chem. Soc. 103, 1088 (1913).
3. V. A. Izmailsky, Report of the All-Union Conference of June 11?14, 1951, Stenographic Record 144, Acad. Sci. USSR Press, 1952.
4. A. N. Terenin, Photochemistry of Dyes. Acad. Sci. USSR Press, 1947, p. 12???.
5. C. C. Baly and I. N. Collie, J. Chem. Soc., 87, 1332 (1905).