1. For [4.n.0] bicyclic system conformational studies, see Refs 6 and 19.
2. Conformation Theory, p. 56. Academic Press, New York (1965).
3. The crystal structure of trans-bicyclo[4,2,0]octyl 1-3,5-dinitrobenzoate
4. and Bull. Soc. Chim. 1366 (1965).
5. and Tetrahedron Lett. 2841 (1976).