Merling, G. (1891), Ueber Tropin. Berichte der deutschen chemischen Gesellschaft, 24: 3108–3126. DOI: 10.1002/cber.189102402151
The Cycloheptatrienylium (Tropylium) Ion W. Von E.Doering, L. H. Knox J. Am. Chem. Soc., 1954, 76 (12), pp. 3203–3206 DOI: 10.1021/ja01641a027
Aromaticity as a Cornerstone of Heterocyclic Chemistry Alexandru T. Balaban, Daniela C. Oniciu, Alan R. Katritzky Chem. Rev., 2004, 104 (5), pp. 2777–2812 DOI: 10.1021/cr0306790
