1. in ?Advances Heterocyclic Chemistry?, Ed. Academic Press, New York, 1963, Vol. 1, p. 189.
2. in ?Comprehensive Organic Chemistry?, Ed. Pergamon, Oxford, 1979, Vol. 4, p.547.
3. in ?Rodd's Chemistry of Carbon Compounds?, 2nd edn., Ed. Elsevier, Amsterdam, 1980, Vol. 4 L, p. 109.
4. in ?Comprehensive Heterocyclic Chemistry?, Ed. Pergamon, Oxford, 1984, Vol. 5, p.875.