Benson Radical Rules for radicals are explicitely given through the center and connecting atoms in the Benson group additivity rules. The method is based on Table 2.14 from Benson's book and corrections given in the literature.
The total thermodynamics is calculated through the Benson rules for all the center atoms, including the radical centers. The other other corrections are for symmetry and steric effects.
The original radical rules from Benson include contributions from carbon, oxygen (bonded to carbon), nitrogen and sulfer. There is also corrections for co radical. Corrections for peroxy radicals are not included in the original rules.