@article{JMLR:v17:15-640,
  author  = {Wenlin Dai and Tiejun Tong and Marc G. Genton},
  title   = {Optimal Estimation of Derivatives in Nonparametric Regression},
  journal = {Journal of Machine Learning Research},
  year    = {2016},
  volume  = {17},
  number  = {164},
  pages   = {1--25},
  url     = {http://jmlr.org/papers/v17/15-640.html}
}