@unpublished{BoeckmannNiebsch2007,
  author  = {Christine B{\"o}ckmann and Jenny Niebsch},
  title   = {Examination of the nonlinear LIDAR-operator : the influence of inhomogeneous absorbing spheres on the operator},
  institution = {Institut f{\"u}r Mathematik},
  series    = {NLD Preprints},
  number    = {47},
  year    = {2007},
}