@book{proakis2004contemporary,

   title={Contemporary communication systems using MATLAB and Simulink},

   author={Proakis, J.G. and Salehi, M. and Bauch, G.},

   isbn={9780534406172},

   lccn={31054410},

   series={BookWare companion series},

   url={http://books.google.at/books?id=5mXGQgAACAAJ},

   year={2004},

   publisher={Thomson--Brooks/Cole}

 }

 @book{oppenheim2010discrete,

   title={Discrete-time signal processing},

   author={Oppenheim, A.V. and Schafer, R.W.},

   isbn={9780131988422},

   series={Prentice-Hall signal processing series},

   url={http://books.google.at/books?id=mYsoAQAAMAAJ},

   year={2010},

   publisher={Prentice Hall}

 }

 @manual{wenzel2011system,

 	title={The Isabelle System Manual},

 	author={Wenzel, M. and Berghofer, S.},

 	organization={TU München},

 	year={2011},

 	month={January}

 }