Write "j'th" in listing comment

chapters/arrays.tex

@@ -971,8 +971,8 @@ \section{Array Indexing}\label{array-indexing}
 \begin{example}
 Array indexing expressions:
 \begin{lstlisting}[language=modelica]
-a[:, j]      // Vector of the j:th column of a.
-a[j]         // Vector of the j:th row of a. Same as: a[j, :]
+a[:, j]      // Vector of the j'th column of a.
+a[j]         // Vector of the j'th row of a. Same as: a[j, :]
 a[j : k]     // Same as: {a[j], a[j+1], $\ldots$, a[k]}
 a[:, j : k]  // Same as: [a[:, j], a[:, j+1], $\ldots$, a[:, k]]
 \end{lstlisting}