@article{JMLR:v15:lan14a,
  author  = {Andrew S. Lan and Andrew E. Waters and Christoph Studer and Richard G. Baraniuk},
  title   = {Sparse Factor Analysis for Learning and Content Analytics},
  journal = {Journal of Machine Learning Research},
  year    = {2014},
  volume  = {15},
  number  = {57},
  pages   = {1959--2008},
  url     = {http://jmlr.org/papers/v15/lan14a.html}
}