1. The matrix equation AX−YB=C;Baksalary;Linear Algebra Appl.,1979
2. The group inverse of a block triangular matrix;Hartwig,1987
3. Roth’s equivalence problem in unit regular rings;Hartwig;Proc. Amer. Math. Soc.,1976
4. R.E. Hartwig, J. Luh, Decomposition of an orthogonally complemented atomic unit-regular ring, 1979 (unpublished)
5. On finite regular rings;Hartwig;Pac. J. Math.,1977