Near the beginning of chapter 6 (Equivalence of Logic and Algebra), in the RA -> FO proof, $\varphi{\sigma\theta(e)}(\overline{x})$ should be defined as $(\varphi_e \wedge \theta[\overline{x}])(\overline{x})$, rather than $\varphi_e(\overline{x}) \wedge \theta[\overline{x}]$.
Near the beginning of chapter 6 (Equivalence of Logic and Algebra), in the RA -> FO proof, $\varphi{\sigma\theta(e)}(\overline{x})$ should be defined as $(\varphi_e \wedge \theta[\overline{x}])(\overline{x})$, rather than $\varphi_e(\overline{x}) \wedge \theta[\overline{x}]$.