@Article{leskovec2008planetary,
  author = {Leskovec, J. and Horvitz, E.},
  title  = {Planetary-scale views on a large instant-messaging network},

  year   = {2008},
  number = {},
  url    = {http://scholar.google.de/scholar.bib?q=info:dvYmn_qj6NQJ:scholar.google.com/&output=citation&hl=de&as_sdt=2000&ct=citation&cd=0},

  const  = {\ text}
}
@Inproceedings{1367620,
  author = {Leskovec, Jure and Horvitz, Eric},
  title  = {Planetary-scale views on a large instant-messaging network},

  year   = {2008},
  number = {},
  url    = {http://portal.acm.org/citation.cfm?id=1367620},
  doi = {http://doi.acm.org/10.1145/1367497.1367620},
  const  = {\ text}
}