1. Linear transformations on matrices: The invariance of rank k matrices;Beasley;Linear Algebra and Appl.,1970
2. LeRoy B. Beasley, Linear transformations on matrices: The invariance of sets of ranks, Can. J. Math, to appear.
3. A Survey of Matrix Theory and Matrix Inequalities;Marcus,1964
4. Spaces of linear transformations of equal rank;Westwick;Linear Algebra and Appl.,1972
5. R. Westwick, Results on rank 3 spaces, unpublished.