@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}}
}