A perturbative contribution to the three-point connected correlation , as in Eq. (A.4). The big red circles corresponds to the three nonlinear density contrasts , , and . The small black dots represent the linear fields  and the Gaussian average amounts to connect them by the linear correlation , shown by the blue solid lines. There are n₁₁, n₂₂, and n₃₃ internal lines within the circles , , and . There are n₁₂, n₁₃, and n₂₃ lines connecting the three circles. Here we have  {n₁₁,n₂₂,n₃₃}  =  {2,2,3}  and  {n₁₂,n₁₃,n₂₃}  =  {3,2,4} . This is part of , which involves the kernels , , and .