@unpublished{FeudelSeehaferSchmidtmann2007,
  author  = {Fred Feudel and Norbert Seehafer and Olaf Schmidtmann},
  title   = {Fluid helicity and dynamo bifurcations},
  institution = {Institut f{\"u}r Physik und Astronomie},
  series    = {NLD Preprints},
  number    = {18},
  year    = {2007},
}