@article{JMLR:v20:17-373,
  author  = {Yichen Chen and Yinyu Ye and Mengdi Wang},
  title   = {Approximation Hardness for A Class of Sparse Optimization Problems},
  journal = {Journal of Machine Learning Research},
  year    = {2019},
  volume  = {20},
  number  = {38},
  pages   = {1--27},
  url     = {http://jmlr.org/papers/v20/17-373.html}
}