Mention where 'actual equations' can be found.

doc/handbook/5_models.tex

 \section{Models}
 Here the basic definitions, the general models concept, and a list of
-models available in \Dumux are given.
+models available in \Dumux are given. The actual differential equations
+can be found in the localresiduals (see doxygen documentation of the
+model's \texttt{LocalResidual} class).
 
 \subsection{Basic Definitions and Assumptions}
 The basic definitions and assumptions are made, using the example
@@ -134,7 +136,7 @@ Dalton's law assumes that the gases in the mixture are non-interacting (with eac
 p = \sum_{i}^{}p_i.
 \end{equation}
 Here $p_i$ refers to the partial pressure of component i.
-As an example, if two equal volumes of gas A and gas B are mixed, the volume of the mixture stays the same but the pressures add up (see Figure \ref{fig:dalton1}). 
+As an example, if two equal volumes of gas A and gas B are mixed, the volume of the mixture stays the same but the pressures add up (see Figure \ref{fig:dalton1}).
 %
 \begin{figure}[ht]
 	\centering
@@ -154,7 +156,7 @@ or for an arbitrary number of gases:
 \end{equation}
 %
 \subsubsection{Amagat's law}
-Amagat's law assumes that the volumes of the component gases are additive; the interactions of the different gases are the same as the average interactions of the components. This is known as Amagat's law: 
+Amagat's law assumes that the volumes of the component gases are additive; the interactions of the different gases are the same as the average interactions of the components. This is known as Amagat's law:
 %
 \begin{equation}
 V = \sum_{i}^{}V_i.
@@ -171,7 +173,7 @@ As an example, if two volumes of gas A and B at equal pressure are mixed, the pr
 %
 The density of the mixture, $\varrho$, can be calculated as follows:
 \begin{equation}
-\varrho = \frac{m}{V} = \frac{m}{V_\mathrm{A} + V_\mathrm{B}} = \frac{m}{\frac{m_\mathrm{A}}{\varrho_\mathrm{A}} \frac{m_\mathrm{B}}{\varrho_\mathrm{B}}} = 
+\varrho = \frac{m}{V} = \frac{m}{V_\mathrm{A} + V_\mathrm{B}} = \frac{m}{\frac{m_\mathrm{A}}{\varrho_\mathrm{A}} \frac{m_\mathrm{B}}{\varrho_\mathrm{B}}} =
 \frac{m}{\frac{X_\mathrm{A} m}{\varrho_\mathrm{A}} \frac{X_\mathrm{B} m}{\varrho_\mathrm{B}}} = \frac{1}{\frac{X_\mathrm{A}}{\varrho_\mathrm{A}} \frac{X_\mathrm{B}}{\varrho_\mathrm{B}}},
 \end{equation}
 %
@@ -182,7 +184,7 @@ or for an arbitrary number of gases:
 \end{equation}
 %
 \subsubsection{Ideal gases}
-An ideal gas is defined as a gas whose molecules are spaced so far apart that the behavior of a molecule is not influenced by the presence of other molecules. 
+An ideal gas is defined as a gas whose molecules are spaced so far apart that the behavior of a molecule is not influenced by the presence of other molecules.
 This assumption is usually valid at low pressures and high temperatures. The ideal gas law states that, for one gas:
 %
 \begin{equation}
@@ -193,7 +195,7 @@ Using the assumption of ideal gases and either Dalton's law or Amagat's law lead
 %
 \begin{equation}
 \varrho = \frac{p}{RT} \sum_{i}^{}M_i x_i ; \quad \varrho_m = \frac{p}{RT}.
-\end{equation} 
+\end{equation}
 %
 \subsection{Available Models}
 A list of all available models can be found
@@ -203,7 +205,7 @@ The documentation includes a detailed description for every model.
 
 \subsubsection{Time discretization}
 
-Our systems of partial differential equations are discretized in space and in time. 
+Our systems of partial differential equations are discretized in space and in time.
 
 Let us consider the general case of a balance equation of the following form
 \begin{equation}\label{eq:generalbalance}