This project contains implementation of two methods and a document with detailed explanation of linear shrinkage along with introduction to the problem of covariance estimation.
"Improved Estimation of the Covariance Matrix of Stock Returns With an Application to Portfolio Selection / Ledoit and Wolf 2001"
http://www.econ.uzh.ch/en/people/faculty/wolf/publications.html
"Direct Nonlinear Shrinkage Estimation of Large-Dimensional Covariance Matrices / Ledoit and Wolf 2017"