@book{Weber1999,
  author    = {Max Weber},
  title     = {Ausgew{\"a}hlte Schriften : Potsdamer Internet-Ausgabe (PIA)},
  editor    = {Elisabeth Flitner},
  url       = {http://www.uni-potsdam.de/u/paed/pia/index.htm},
  year      = {1999},
}