Distribution function of multiple trees

The free energy change on passing from the reference state to the final solution, at equilibrium with respect to cluster formation, is 

the free energy change A(j l) accompanying the formation of a (j l)-cluster in a hypothetical undiluted amorphous state from the separate primary molecules in their standard states is defined by 

In the postgel regime, the last term for the gel part is necessary [9,26], 

By differentiating the free energy, we find the chemical potential 

Substituting the result (7.86) back into the starting free energy (7.79), we find it in the form of (5.37), where the association part is given by 

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