More stable links for openprod

Closes modelica#3055

chapters/revisions.tex

@@ -1715,15 +1715,15 @@ \subsection{Acknowledgments}\label{acknowledgments2}
 \item
   The Swedish funding agency VINNOVA has partially funded Linköping
   University (PELAB) within the ITEA2 project OPENPROD
-  (http://www.openprod.org).
+  (\url{https://itea4.org/project/openprod.html}).
 \item
   The Swedish Research Council has partially funded Linköping University
   (PELAB) within the project \emph{High-Level Debugging of Equation-Based
   System Modeling \& Simulation Languages}.
 \item
   The German Ministry BMBF has partially funded FH Bielefeld (BMBF
   Förderkennzeichen: 01IS09029C) within the ITEA2 project OPENPROD
-  (\href{http://www.openprod.}{http://www.openprod.org}).
+  (\url{https://itea4.org/project/openprod.html}).
 \end{itemize}
 
 \section{Modelica 3.1}\label{modelica-3-1}