The conditions of stability are the same in the case of networks with scale-free topology where the in-and out-degree distribution is a power-law distribution: P ( K ) ∝ ∝ K − − γ γ , and ⟨ ⟨ K i n ⟩ ⟩ = ⟨ ⟨ K o u t ⟩ ⟩ , since every out-link from a node is an in-link to another.