1. Kirmse, W.: Carbene, Carbenoide und Carbenanaloge. Weinheim/Bergstr.: Verlag Chemie 1969.
2. Gilchrist, T. L., Reeves, C. W.: Carbenes, nitrenes and arynes. London: Th. Nelson and Sons 1969.
3. For a recent summary see: D??rr, H. In: Methoden der Organ. Photochemie, Bd. IV/5, Houben Weyl, in press;
4. Reactions of o-quinone-diazides which undergo Wolff-rearrangement are equally excluded.
5. Gleiter, R., Hoffmann, R.: J. Am. Chem. Soc. 90, 5457 (1968).