@unpublished{GilKrainerMendoza2008,
  author  = {Juan B. Gil and Thomas Krainer and Gerardo A. Mendoza},
  title   = {Geometry and spectra of closed extensions of elliptic cone operators},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(2004) 21},
  year    = {2008},
}