Use the mode expansion of the fermion field, given in eqn (9.7.19), and the anticommutation relations of the operators $A(\theta)$ and $A^{\dagger}(\theta)$, to compute the correlation functions
$$
\begin{aligned}
G_1(x, t) & =\langle 0|\Psi(x, t) \Psi(0,0)| 0\rangle \\
G_2(x, t) & =\langle 0|\bar{\Psi}(x, t) \Psi(0,0)| 0\rangle .
\end{aligned}
$$