@article{JMLR:v14:hennig13a,
  author  = {Philipp Hennig and Martin Kiefel},
  title   = {Quasi-Newton Method: A New Direction},
  journal = {Journal of Machine Learning Research},
  year    = {2013},
  volume  = {14},
  number  = {26},
  pages   = {843--865},
  url     = {http://jmlr.org/papers/v14/hennig13a.html}
}