@unpublished{BraunFeudelSeehafer2007,
  author  = {Robert Braun and Fred Feudel and Norbert Seehafer},
  title   = {Bifurcations and chaos in an array of forced vortices},
  institution = {Institut f{\"u}r Physik und Astronomie},
  series    = {NLD Preprints},
  number    = {37},
  year    = {2007},
}