\documentclass{imsas}
\begin{document}
\fontfamily{phv}

% Roman page numbering
\pagenumbering{roman}
\setcounter{page}{1}

% Insering title page 
\include{titlepage_en.tex}                 % Title page in English
%\include{titlepage.tex}                     % Title page in German

% Insering declaration page
\include{extra/declaration.tex}
% Insering abstract page
\include{extra/abstract.tex}

% Creating table of contents
\tableofcontents
\newpage
% Creating table of figures and tables
\listoffigures
\listoftables
\newpage

\clearpage
% Arabic page numbering
\pagenumbering{arabic}
\setcounter{page}{5}

% Inserting Chapter 1
\include{chapter/chapter_1.tex}
\newpage

% Inserting Chapter 2
\include{chapter/chapter_2.tex}

% Inserting Reference page
\addcontentsline{toc}{section}{References}
\bibliographystyle{plain}
\bibliography{extra/reference}

\end{document}