@unpublished{SchulzeShlapunovTarkhanov2008,
  author  = {Bert-Wolfgang Schulze and Alexander Shlapunov and Nikolai Nikolaevich Tarkhanov},
  title   = {Regularisation of mixed boundary problems},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(1999) 09},
  year    = {2008},
}