I have four lines of equations. The first two and the second two need to be grouped by a left bracket, and all four need to be grouped by one overall left bracket.
I am using an array within an equation. I can't manage to add the two 'inner' left brackets. The one big left bracket over all four equations is not a problem, which is the following:
\begin{equation}
\left\{
\begin{array}{lcl}
1\\
2\\
3\\
4
\end{array}
\right.
\end{equation}
And this seems to work just fine. But when I try the following
\begin{equation}
\left\{
\begin{array}{lcl}
\left\{
\begin{array}{lcl}
1\\
2
\end{array}{lcl}
\right.
\end{array}
\begin{array}{lcl}
\left\{
\begin{array}{lcl}
3\\
4
\end{array}
\right.
\end{array}
\right.
\end{equation}
it doesn't work. I've tried some other changes, including changing to eqnarray, or changing the places of the brackets, but nothing seems to work. Now I am not sure how to solve this.