@unpublished{SavinSternin2008,
  author  = {Anton Savin and Boris Sternin},
  title   = {Index defects in the theory of nonlocal boundary value problems and the η-invariant},
  institution = {Institut f{\"u}r Mathematik},
  series    = {Preprint},
  number    = {(2001) 31},
  year    = {2008},
}