@incollection{OpitzWiedemann1989,
  author    = {Otto Opitz and Raimund Wiedemann},
  title     = {An agglomerative algorithm of overlapping clustering},
  booktitle = {Conceptual and numerical analysis of data: proceedings of the 13th Conference of the Gesellschaft f{\"u}r Klassifikation e. V., University of Augsburg, April 10-12, 1989},
  editor    = {Otto Opitz},
  isbn      = {978-3-540-51641-5},
  doi       = {10.1007/978-3-642-75040-3_13},
  year      = {1989},
}