@TECHREPORT {ESl03a,
     AUTHOR = {{van den Eshof}, Jasper and Sleijpen, Gerard L. G.},
      TITLE = {Accurate conjugate gradient methods for shifted systems},
       TYPE = {Preprint},
     NUMBER = {1265},
INSTITUTION = {Dep. Math., University Utrecht},
    ADDRESS = {Utrecht, the Netherlands},
      MONTH = {January},
       YEAR = {2003},}


@ARTICLE {ESl04a,
  AUTHOR = {{van den Eshof}, J. and Sleijpen, G. L. G.},
   TITLE = {Accurate conjugate gradient methods for 
           families of shifted systems},
 JOURNAL = {Appl. Numer. Math.},
FJOURNAL = {Applied Numerical Mathematics},
  VOLUME = {49/1}, 
    YEAR = {2004},
   PAGES = {17--37},}