How far is the π-electron delocalization of the phenanthrenemoiety modified in the aza-analogues and their N-oxides? Beata T. Stępień, Tadeusz M. Krygowski, a Michał K. Cyrański, Jacek Młochowski, Pierluigi Orioli, and Francesco Abbate Arkivoc 2003 Link
Nucleus-Independent Chemical Shifts: A Simple and Efficient Aromaticity ProbePaul von Ragué Schleyer, Christoph Maerker, Alk Dransfeld, Haijun Jiao, and Nicolaas J. R. van Eikema Hommes J. Am. Chem. Soc.; 1996; 118(26) pp 6317-6318; (Communication) doi:10.1021/ja960582d
25 years of NICS – much more than nothing! Ralph Puchta, Slađana Đorđević, Slavko Radenković, Haijun Jiao, and Nico van Eikema Hommes J. Serb. Chem. Soc.; 2022; 87(12) pp 1439-1446; (Communication) doi:10.2298/JSC211203057P
Definition of aromaticity basing on the harmonic oscillator model Tetrahedron Letters, Volume 13, Issue 36, 1972, Pages 3839-3842 J. Kruszewski and T. M. Krygowski doi:10.1016/S0040-4039(01)94175-9
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What is aromaticity?Paul von Ragué Schleyer and Haijun Jiao Pure Appl. Chem., Vol. 68, No. 2, pp. 209-218, 1996Link