@article{JMLR:v9:crammer08a,
  author  = {Koby Crammer and Michael Kearns and Jennifer Wortman},
  title   = {Learning from Multiple Sources},
  journal = {Journal of Machine Learning Research},
  year    = {2008},
  volume  = {9},
  number  = {57},
  pages   = {1757--1774},
  url     = {http://jmlr.org/papers/v9/crammer08a.html}
}