@unpublished{DyachenkoTarkhanov2014,
  author  = {Evgueniya Dyachenko and Nikolai Nikolaevich Tarkhanov},
  title   = {Singular perturbations of elliptic operators},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprints des Instituts f{\"u}r Mathematik der Universit{\"a}t Potsdam},
  number    = {3 (2014) 1},
  pages     = {21},
  year    = {2014},
}