Updates to add in robin boundary condition assignment at end of tutorial

basics/helmholtz/basics-helmholtz.tex

@@ -513,6 +513,7 @@ You should be now familiar with the following topics:
 \item If the solver is compiled with the MPI option, then try running the case in parallel 
 with \inlsh{mpirun -np 2}.
 \item Change the Projection Operator to DisContinuous to see the same problem running with an HDG solver.
+\item Change one of the boundary conditiosn to a Robin (Mixed) boundary condition of the form $\partial u/partial n = \alpha u + \beta$ whith $\alpha =1$ and $\beta$ determined from the exact solution. 
 \end{enumerate}
 
 \begin{tipbox}