@unpublished{MakhmudovTarkhanov2013,
  author  = {Olimdjan Makhmudov and Nikolai Nikolaevich Tarkhanov},
  title   = {An extremal problem related to analytic continuation},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprints des Instituts f{\"u}r Mathematik der Universit{\"a}t Potsdam},
  number    = {2 (2013) 4},
  year    = {2013},
}