@book{Steinhausen1977,
  author    = {Steinhausen, Detlef},
  title     = {Clusteranalyse},
  edition   = {1. Aufl.},
  publisher = {de Gruyter},
  address   = {Berlin [u.a.]},
  isbn      = {3-11-007054-5},
  pages     = {206 S. : graph. Darst.},
  year      = {1977},
  language  = {de}
}
@incollection{Stiegler1977,
  author    = {Stiegler, Roland},
  title     = {Fernstudienlehrgang f{\"u}r evangelische Religionslehrer. Studienbrief 10: Herbert Schultze, Probleme der Gewissenserziehung},
  series = {Deutsches Institut f{\"u}r Fernstudien},
  booktitle = {Deutsches Institut f{\"u}r Fernstudien},
  address   = {T{\"u}bingen},
  year      = {1977},
  language  = {de}
}