(X0) -- (X1) node [midway] {$\gradtm$};
\path[draw, arr] (X1) -- (X2) node [midway] {$\curltm$};
\path[draw, arr] (X2) -- (X3) node [midway] {$\divergtm$};
%
\path[draw, arr] (R) -- (X0);
\path[draw, arr] (X3) -- (Z);
\end{tikzpicture}
%%\includegraphics{img/de_rham/de_rham_2D_grad_rot_cont}\fsp,
\end{split}$$ In [@oh:2015 Theorem 2.1], it has been proven that the sequence is exact for $m\neq0$, meaning that the range of each operator linking two spaces is equal to the kernel of the subsequent one. The use of discretizations that respect the above structure is necessary to yield stable numerical methods. The aim of the following sections is to present a technique to build such discretizations, which are well-suited for the resolution of problems in electromagnetism.

Discretization {#sec:discretization}
==============

To solve numerical problems in electromagnetism, we need to approximate the continuous spaces $\Zsp^{m, \, k}$, $k=0,\, \ldots, \,
3$ by means of finite-dimensional subspaces $\Zsp_h^{m, \, k}$ which depend on a discretization parameter related to the characteristic element size $h$. In the following, we will use the subscript $h$ to refer to quantities related to the finite-dimensional spaces and we will consider conforming discretizations, meaning that $\Zsp_h^{m, \,
    k} \subset \Zsp^{m, \, k}$ for every value of $h$. In this section, we mimic the strategy 