diff --git a/doc/documentation.tex b/doc/documentation.tex
index feec262..184bd9a 100644
--- a/doc/documentation.tex
+++ b/doc/documentation.tex
@@ -1,3 +1,73 @@
+% *======================================================================*
+%  Cactus Thorn template for ThornGuide documentation
+%  Author: Ian Kelley
+%  Date: Sun Jun 02, 2002
+%  $Header$
+%
+%  Thorn documentation in the latex file doc/documentation.tex
+%  will be included in ThornGuides built with the Cactus make system.
+%  The scripts employed by the make system automatically include
+%  pages about variables, parameters and scheduling parsed from the
+%  relevant thorn CCL files.
+%
+%  This template contains guidelines which help to assure that your
+%  documentation will be correctly added to ThornGuides. More
+%  information is available in the Cactus UsersGuide.
+%
+%  Guidelines:
+%   - Do not change anything before the line
+%       % START CACTUS THORNGUIDE",
+%     except for filling in the title, author, date, etc. fields.
+%        - Each of these fields should only be on ONE line.
+%        - Author names should be separated with a \\ or a comma.
+%   - You can define your own macros, but they must appear after
+%     the START CACTUS THORNGUIDE line, and must not redefine standard
+%     latex commands.
+%   - To avoid name clashes with other thorns, 'labels', 'citations',
+%     'references', and 'image' names should conform to the following
+%     convention:
+%       ARRANGEMENT_THORN_LABEL
+%     For example, an image wave.eps in the arrangement CactusWave and
+%     thorn WaveToyC should be renamed to CactusWave_WaveToyC_wave.eps
+%   - Graphics should only be included using the graphicx package.
+%     More specifically, with the "\includegraphics" command.  Do
+%     not specify any graphic file extensions in your .tex file. This
+%     will allow us to create a PDF version of the ThornGuide
+%     via pdflatex.
+%   - References should be included with the latex "\bibitem" command.
+%   - Use \begin{abstract}...\end{abstract} instead of \abstract{...}
+%   - Do not use \appendix, instead include any appendices you need as
+%     standard sections.
+%   - For the benefit of our Perl scripts, and for future extensions,
+%     please use simple latex.
+%
+% *======================================================================*
+%
+% Example of including a graphic image:
+%    \begin{figure}[ht]
+% 	\begin{center}
+%    	   \includegraphics[width=6cm]{MyArrangement_MyThorn_MyFigure}
+% 	\end{center}
+% 	\caption{Illustration of this and that}
+% 	\label{MyArrangement_MyThorn_MyLabel}
+%    \end{figure}
+%
+% Example of using a label:
+%   \label{MyArrangement_MyThorn_MyLabel}
+%
+% Example of a citation:
+%    \cite{MyArrangement_MyThorn_Author99}
+%
+% Example of including a reference
+%   \bibitem{MyArrangement_MyThorn_Author99}
+%   {J. Author, {\em The Title of the Book, Journal, or periodical}, 1 (1999),
+%   1--16. {\tt http://www.nowhere.com/}}
+%
+% *======================================================================*
+
+% If you are using CVS use this line to give version information
+% $Header$
+
 \documentclass{article}
 
 % Use the Cactus ThornGuide style file
@@ -8,14 +78,62 @@
 
 \begin{document}
 
-\title{ExternalLibraries/MPI}
+% The author of the documentation
+\author{Federico Cipolletta, Roland Haas}
+
+% The title of the document (not necessarily the name of the Thorn)
+\title{MPI}
+
+% the date your document was last changed, if your document is in CVS,
+% please use:
+%    \date{$ $Date$ $}
+% when using git instead record the commit ID:
+%    \date{$ $Id$ $}
+% and add this line to your repos' .gitattributes file:
+% **.tex ident
+\date{2020-07-01}
 
 \maketitle
 
 % Do not delete next line
 % START CACTUS THORNGUIDE
 
+% Add all definitions used in this documentation here
+%   \def\mydef etc
+
+% Add an abstract for this thorn's documentation
+\begin{abstract}
+This thorn provides access to the MPI library.
+\end{abstract}
+
+% The following sections are suggestive only.
+% Remove them or add your own.
+
+\section{Using This Thorn}
+
+Refer to the Cactus UserGuide, Sec. B2.2, in order to know how this thorn can be used in a compiled configuration and how to possibly linking another specific version, already installed steparately.
+
+\subsection*{Note on possible ExternalLibraries' location stripping}
+\label{stripping}
+
+Each thorn contained in \texttt{Cactus/arrangements/ExternalLibraries} will automatically adopt the library version contained in the \texttt{Cactus/arrangements/<library>/dist} folder. In particular, the tarball in \texttt{Cactus/arrangements/<library>/dist} is only used if either \texttt{THORN\_DIR} is set to \texttt{BUILD} or is left empty and no precompiled copy of the library is found. If another location is specified via the \texttt{THORN\_DIR} variable in the \texttt{<machine>.cfg} file at compilation, then the \texttt{Cactus/lib/sbin/strip-incdirs.sh} script will automatically strip away (for safety reasons) the locations:
+\begin{Lentry}
+\item [\texttt{/include}]
+\item [\texttt{/usr/include}]
+\item [\texttt{/usr/local/include}]
+\end{Lentry}
+from \texttt{THORN\_INC\_DIRS} which default to \texttt{THORN\_DIR/include}. Therefore, if there is any need for using one already installed version of one external library, the aforementioned location should be avoided (e.g. indicating \texttt{/home} as the \texttt{THORN\_DIR} will work with no problems if the required library is installed there) or should be carefully checked, in order to avoid unwanted stripping. The same stripping happens to \texttt{THORN\_LIB\_DIRS} in \texttt{lib/sbin/strip-libdirs.sh} with a larger list of directories:
+\begin{Lentry}
+\item [\texttt{/lib}]
+\item [\texttt{/usr/lib}]
+\item [\texttt{/usr/local/lib}]
+\item [\texttt{/lib64}]
+\item [\texttt{/usr/lib64}]
+\item [\texttt{/usr/local/lib64}] 
+\end{Lentry}
+
 % Do not delete next line
 % END CACTUS THORNGUIDE
 
 \end{document}
+