@article{nonconvexstatisticaloptimizationminimax,
  title = {Nonconvex Statistical Optimization: Minimax-Optimal Sparse PCA in Polynomial Time},
  author = {Zhaoran Wang and Huanran Lu and Han Liu},
  year = {2014},
  eprint = {1408.5352},
  archivePrefix = {arXiv},
  url = {http://arxiv.org/abs/1408.5352v1},
}