@incollection {SarkisPhD,
  AUTHOR = {Sarkis, Marcus},
  TITLE = {{S}chwarz preconditioners for elliptic problems with discontinuous
coefficients using conforming and non-conforming elements},
   booktitle = {PhD Dissertation, Technical Report 671},
publisher =  {Courant Institute},
 Month = {September}, 
  YEAR = {1994},
}