diff --git a/chapters/synchronous.tex b/chapters/synchronous.tex
index 230e40d4b..655bfd651 100644
--- a/chapters/synchronous.tex
+++ b/chapters/synchronous.tex
@@ -471,6 +471,8 @@ \section{Clock Constructors}\label{clock-constructors}
 \end{semantics}
 \end{operatordefinition*}
 
+\subsection{Restrictions on Clocks in a Base-Partition}\label{restrictions-on-clocks-in-a-base-partition}
+
 Besides inferred clocks and solver clocks, one of the following mutually exclusive associations of clocks are possible in one base-partition:
 \begin{enumerate}
 \item
@@ -495,6 +497,8 @@ \section{Clock Constructors}\label{clock-constructors}
   \end{nonnormative}
 \end{enumerate}
 
+\subsection{Restrictions on Clock Variables}\label{restrictions-on-clock-variables}
+
 Clock variables can be used in a restricted form of expressions.
 Generally, every expression switching between clock variables must be an evaluable expression (in order that clock analysis can be performed when translating a model).
 Thus subscripts on clock variables and conditions of if-then-else switching between clock variables must be evaluable expressions, and there are similar restrictions for sub-clock conversion operators \cref{sub-clock-conversion-operators}.