or alternatively as the second derivative of an energy functional
that then also yields the residual itself.
-\item \texttt{step-74} SIPG for the Poisson equation \todo[inline]{TODO}
+\item \texttt{step-74} implements the symmetric interior penalty Galerkin
+(SIPG) method for Poisson's equation using the \texttt{FEInterfaceValues} class
+in combination with \texttt{MeshWorker::mesh\_loop()}. With \texttt{FEInterfaceValues},
+we can directly obtain the jump and the average of shape functions and of the solution
+across cell faces, which simplifies the assembling of face terms in DG methods especially on
+adaptive meshes.
+
\item \texttt{step-75} demonstrates a state-of-the-art way of solving a simple
Laplace problem using $hp$-adaptation and hybrid multigrid methods on machines