@article{JMLR:v17:15-320,
  author  = {Jiazhong Nie and Wojciech Kotlowski and Manfred K. Warmuth},
  title   = {Online PCA with Optimal Regret},
  journal = {Journal of Machine Learning Research},
  year    = {2016},
  volume  = {17},
  number  = {173},
  pages   = {1--49},
  url     = {http://jmlr.org/papers/v17/15-320.html}
}