1. Ueber die Beziehungen der Zimmtsäure zu der Indigogruppe
2. R. J. Sundberg , ‘The Chemistry of Indoles’, Academic Press, New York, 1970, Chapter III.
3. R. K. Brown , ‘Indoles, The Chemistry of Heterocyclic Compounds’, ed. W. J. Houlihan, Interscience, 1972, Vol. 25, part 1, Chapter II.
4. R. J. Sundberg , in ‘Comprehensive Heterocyclic Chemistry’, ed. A. R. Katritzky, C. W. Rees, C. W. Bird, and G. W. H. Cheeseman, Pergamon, Oxford, 1984, Vol. 4, pp. 313–376.
5. G. P. Ellis , in ‘The Chemistry of Heterocyclic Compounds’, Wiley, Chichester, 1992, Vol. 47, part 2.