@book{Tietze1992,
  author    = {Tietze, J{\"u}rgen},
  title     = {Monotonie und Kr{\"u}mmung : Wechselbeziehungen bei Gesamtkosten- und St{\"u}ckkostenfunktionen},
  publisher = {Alano-Verl.},
  address   = {Aachen},
  isbn      = {3-89399-169-7},
  pages     = {VI, 51 S. : zahlr. graph. Darst.},
  year      = {1992},
  language  = {de}
}
@book{Tietze1992,
  author    = {Tietze, J{\"u}rgen},
  title     = {{\"O}konomische Interpretation optimaler Simplex-Tableaus},
  publisher = {Alano-Verl.},
  address   = {Aachen},
  isbn      = {3-89399-170-0},
  pages     = {VI, 33 S.},
  year      = {1992},
  language  = {de}
}