@book{JonasLanger1994,
  author    = {Peter Jonas and Heinz Langer},
  title     = {Selfadjoint extensions of a closed linear realtion of defect one in a Krein space. Universit{\"a}t Potsdam, Fachbereich Mathematik},
  volume    = {1994, 17},
  year      = {1994},
}