Diagrams associated with the standard perturbation theory as obtained from a path-integral formalism up to 1-loop order for the three-point correlation C₃. Although they are different from those obtained by the standard approach, their sum at each order is identical to the sum of the standard diagrams of the same order over P_L(k). The lines are the linear two-point correlation C_L (blue solid line) and the linear response R_L (red solid line with an arrow). The black dots are the three-leg vertex K_s that enters the quadratic term of the equation of motion. The numbers are the multiplicity factors of each diagram. The tree-order diagram a) gives Eq. (39), for the density bispectrum, while the 1-loop diagrams b), ..., i), give the contribution of order .