@unpublished{Michel1996,
  author  = {Volker Michel},
  title   = {Singular Optimal Control - The State of the Art},
  institution = {Fachbereich Mathematik},
  series    = {Berichte der Arbeitsgruppe Technomathematik (AGTM Report)},
  number    = {169},
  year    = {1996},
  url  = {http://nbn-resolving.de/urn:nbn:de:hbz:386-kluedo-5725},
}