@article{hennig13,
  title = {Quasi-Newton Methods: A New Direction},
  author = {Hennig, Philipp and Kiefel, Martin},
  journal = {Journal of Machine Learning Research},
  volume = {14},
  number = {1},
  pages = {843--865},
  month = mar,
  year = {2013},
  url = {http://www.jmlr.org/papers/volume14/hennig13a/hennig13a.pdf},
  month_numeric = {3}
}