@TechReport{TR028,
  author =	 "Dieter Willersinn",
  institution =	 "PRIP, TU Wien",
  number =	 "PRIP-TR-028",
  title =	 "Parallel {G}raph {C}ontraction for {D}ual
                  {I}rregular {P}yramids",
  year =	 "1994",
  url =		 "https://www.prip.tuwien.ac.at/pripfiles/trs/tr28.pdf",
  abstract =	 "Hierarchical representation of images is a crucial
                  building principle of a system architecture that can
                  cope with the complexity of visual perception. This
                  paper presents an algorithm that builds a hierarchy
                  which is flexible enough to provide a shift and
                  scale invariant abstract representation of image
                  content. The hierarchy is irregular in the sense
                  that an element of the representation may have an
                  arbitrary number of neighbors. At the same time, the
                  representation can be described by a bounded data
                  structure. Main properties of the algorithm with
                  respect to visual perception are proved.",
}