@Article{Butler:2008:Nature:18172465,
  author = {Butler, D},
  title  = {Free journal-ranking tool enters citation market},
  journal = {Nature},
  year   = {2008},
  number = {7174},
  url    = {http://www.nature.com/news/2008/080102/full/451006a.html},
  doi = {10.1038/451006a},
  const  = {\ text}
}