@Book{Heuser:1986,

   author = 	 {H. Heuser},

   title = 	 {Funktionalanalysis: Theorie und Anwendung},

   publisher = 	 {Teubner},

   year = 	 1986

 }

 @InCollection{Narici:1996,

   author = 	 {L. Narici and E. Beckenstein},

   title = 	 {The {Hahn-Banach Theorem}: The Life and Times},

   booktitle = 	 {Topology Atlas},

   publisher =	 {York University, Toronto, Ontario, Canada},

   year =	 1996,

   note =	 {\url{http://at.yorku.ca/topology/preprint.htm} and

                   \url{http://at.yorku.ca/p/a/a/a/16.htm}}

 }

 @Article{Nowak:1993,

   author =       {B. Nowak and A. Trybulec},

   title =	 {{Hahn-Banach} Theorem},

   journal =      {Journal of Formalized Mathematics},

   year =         {1993},

   volume =       {5},

   institution =  {University of Bialystok},

   note =         {\url{http://mizar.uwb.edu.pl/JFM/Vol5/hahnban.html}}

 }