1. E.O. Fischer, A. Maasböl, Angew. Chem. 76 (1964) 645; Angew. Chem. Int. Ed. Engl. 3 (1964) 580.
2. For an excellent book, which has been dedicated to Prof. Dr. E.O. Fischer on the occasion of his 65th birthday and which covers the older literature, see: K.H. Dötz, H. Fischer, P. Hofmann, F.R. Kreissl, U. Schubert, K.Weiss, Transition Metal Carbene Complexes, VCH Publishers, Weinheim, Germany, 1983.
3. J. Organomet. Chem. 617–618 (2001), Special Issue “Transition Metal Complexes of Carbenes and Related Species in 2000” (Ed.: G. Bertrand).
4. W.A. Herrmann, Angew. Chem. 86 (1974) 556; Angew. Chem. Int. Ed. Engl. 13 (1974) 599.