A mathematical process of enumeration of Kekule structures of any polybenzenoïd monoradical having only zig-zag assemblies of benzenoid hydrocarbons is given by using a method which consisted of the excision of the radical center C° in order to obtain a conjugated hydrocarbon having a 12-annulene core ring appended to one or more polybenzenoïd fragments and the partition of the resulting conjugated hydrocarbon into smaller independent resonant circuits.