@unpublished{Schulze2008,
  author  = {Bert-Wolfgang Schulze},
  title   = {An algebra of boundary value problems not requiring Shapiro-Lopatinskil conditions},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(1999) 24},
  year    = {2008},
}