@Article{SCI:Sch2008a,
  author =    "C.E. Scheidegger and D. Koop and E. Santos and
              H.T. Vo and S.P. Callahan and J. Freire and C.T.
              Silva.",
  title =     "Tackling the Provenance Challenge One Layer at a
              Time",
  journal =   "Concurrency Computat.: Pract. Exper.",
  volume =    "20",
  number =    "5",
  pages =     "473--483",
  year =      "2008",
  keywords =  "vistrails, provenance, , vistrails, vacet",
  url =       "http://www.sci.utah.edu/publications/scheidegger07/tackling.pdf",
}