Fix typos in Isomorphic Structures

Author: FnControlOption

content/model-theory/basics/isomorphism.tex

@@ -10,7 +10,7 @@
 \olsection{Isomorphic Structures}
 
 First-order !!{structure}s can be alike in one of two ways. One way in
-which the can be alike is that they make the same !!{sentence}s
+which they can be alike is that they make the same !!{sentence}s
 true. We call such !!{structure}s \emph{elementarily equivalent}. But
 structures can be very different and still make the same !!{sentence}s
 true---for instance, one can be !!{enumerable} and the other not.
@@ -117,8 +117,8 @@
 \end{prob}
 
 \begin{defn}
-An \emph{automorphism} of a structure $\mathfrak{M}$ is an isomorphism
-of $\mathfrak{M}$ onto itself.
+An \emph{automorphism} of a structure $\Struct{M}$ is an isomorphism
+of $\Struct{M}$ onto itself.
 \end{defn}
 
 \begin{prob}