Based on Charlesby's definition of the sol quantity

the parameters for the internal structure of the cross-linking polymer were calculated for the cases of the initial molecular weight distribution of Flory and of Schulz type. The sol portion should give no contributions to the swelling and the equilibrium elastic modulus of the cross-linked sample

and the free chain ends of the gel molecules should be taken into consideration. Revised formulae for the swelling and the elastic properties of cross-linked polymers are presented.