1. For reviews on the Norrish-Yang reaction, see:
2. Synthetic Organic Photochemistry (Molecular and Supramolecular Photochemistry), Vol. 12 (Eds.: A. G. Griesbeck, J. Mattay), Marcel Dekker, New York, 2005, pp. 11-39 and 41-87;
3. Handbook of Organic Photochemistry and Photobiology, Vol. 1, 2nd ed. (Eds.: W. M. Horspool, F. Lenci), CRC, Boca Raton, 2003, chap. 52, 55, 57, and 58;
4. 1,5-Biradicals and five-membered rings generated by .delta.-hydrogen abstraction in photoexcited ketones