%% 
%%  Example 04-01-4 
%%  Copyright (C) 2016 Herbert Voss
%% 
%% ==== 
% Show page(s) 1
%% 
%% 
\documentclass[]{screxa}
\pagestyle{empty}
\setlength\textwidth{328.62788pt}
\setlength\parindent{0pt}
%StartShownPreambleCommands
\usepackage{amsmath,bigdelim}
%StopShownPreambleCommands
\begin{document}
\[
  \begin{pmatrix}
     & x_{11} & x_{12} & \dots & x_{1p} & \rdelim\}{4}{3cm}[some text]\\
     \ldelim[{5}{1cm}[text] & x_{21} & x_{22} & \dots & x_{2p} \\
     & \vdots\\
     & x_{n_1 1}& x_{n_1 2} & \dots & x_{n_1 p}\\
     & x_{n_1+1,1}&x_{n_1+1,2} & \dots & x_{n_1+1, p} &
         \rdelim\}{3}{3cm}[some more text]\\
     & \vdots\\
     & x_{n_1+n_2, 1} & x_{n_1+n_2,2} & \dots & x_{n_1+n_2,p}\\
     & \vdots \\
  \end{pmatrix}
\]
\end{document}
