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  year   = {2010},
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  url    = {http://scans.hebis.de/HEBCGI/show.pl?22114256_aub.html},

  const  = {\ text}
}
@Inproceedings{zhang1996birch,
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  title  = {BIRCH: An Efficient Data Clustering Method for Very Large Databases},

  year   = {1996},
  number = {},
  url    = {http://doi.acm.org/10.1145/233269.233324},
  doi = {10.1145/233269.233324},
  const  = {\ text}
}
@Book{deininger1992studienarbeiten,
  author = {Deininger, Marcus and Lichter, Horst and Ludewig, Jochen and Schneider, Kurt},
  title  = {Studien-Arbeiten ein Leitfaden zur Vorbereitung, Durchführung und Betreuung von Studien-, Diplom- und Doktorarbeiten am Beispiel Informatik},

  year   = {1992},
  number = {},
  url    = {http://link.springer.com/book/10.1007/978-3-322-99375-5},

  const  = {\ text}
}
@Book{mehlhorn1988datenstrukturen,
  author = {Mehlhorn, Kurt},
  title  = {Datenstrukturen und effiziente Algorithmen 1: Sortieren und Suchen},

  year   = {1988},
  number = {},
  url    = {http://hds.hebis.de/ubks/Record/HEB00611184X},

  const  = {\ text}
}