@inproceedings{jianqing2012vast,
  title={Vast volatility matrix estimation using high-frequency data for portfolio selection},
  author={Jianqing Fan, Yingying Li, and Ke Yu},
  url={http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191221113551746320859},
  booktitle={Journal of the American Statistical Association},
  volume={107},
  number={497},
  pages={412-428},
  year={2012},
}
             
            
                
Jianqing Fan, Yingying Li, and Ke Yu. Vast volatility matrix estimation using high-frequency data for portfolio selection. 2012. Vol. 107. In Journal of the American Statistical Association. pp.412-428. http://archive.ymsc.tsinghua.edu.cn/pacm_paperurl/20191221113551746320859.