@unpublished{SchroheSeiler2008,
  author  = {Elmar Schrohe and J{\"o}rg Seiler},
  title   = {Ellipticity and invertibility in the cone algebra on Lp-Sobolev spaces},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(1999) 28},
  year    = {2008},
}