@article{oai:tsukuba.repo.nii.ac.jp:00015738, author = {Takemura, Akimichi}, issue = {2}, journal = {Tsukuba Journal of Mathematics}, month = {Dec}, pages = {367--376}, title = {An orthogonally invariant minimax estimator of the covariance matrix of a multivariate normal population}, volume = {8}, year = {1984} }