General description of ultraviolet divergences in the \(\phi ^4_4\) model. Loop and one-particle irreducible (1PI) diagrams. The superficial degree of divergence. Renormalization of the one-loop contribution to the four-point Green’s function (the sunset diagram). The BPHZ subtraction scheme. Lorentz invariant renormalization of the two-point Green’s function. The renormalization constants \(Z_1, Z_3, \delta m^2\) and the multiplicative renormalization.