--- a/slides/slides04.tex	Tue Oct 03 23:23:57 2023 +0100
+++ b/slides/slides04.tex	Thu Oct 05 10:31:05 2023 +0100
@@ -279,7 +279,7 @@
 OP:\\
 \hspace{5mm}\texttt{"+"}, \texttt{"-"}\\
 NUM:\\
-\hspace{5mm}(NONZERODIGIT $\cdot$ DIGIT$^*$) + {''0''}\\
+\hspace{5mm}(NONZERODIGIT $\cdot$ DIGIT$^*$) + {"0"}\\
 NUMBER:\\
 \hspace{5mm}NUM +  (\texttt{"-"} $\cdot$ NUM)\\
 \end{tabular}