@unpublished{SultanovKalyakinTarkhanov2014,
  author  = {Oskar Sultanov and Leonid Kalyakin and Nikolai Nikolaevich Tarkhanov},
  title   = {Elliptic perturbations of dynamical systems with a proper node},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprints des Instituts f{\"u}r Mathematik der Universit{\"a}t Potsdam},
  number    = {3 (2014) 4},
  pages     = {12},
  year    = {2014},
}