@Inproceedings{koren2009collaborative,
  author = {Koren, Yehuda},
  title  = {Collaborative filtering with temporal dynamics},

  year   = {2009},
  number = {},
  url    = {http://doi.acm.org/10.1145/1557019.1557072},
  doi = {10.1145/1557019.1557072},
  const  = {\ text}
}