Pseudo-similarity and partial unit regularity Frank J. Hall; Robert E. Hartwig; Irving Jack Katz; Morris Newman — 1983 Czechoslovak Mathematical Journal
Some properties of the q -adic Vandermonde matrix. Mani, Vaidyanath; Hartwig, Robert E. — 1996 ELA. The Electronic Journal of Linear Algebra [electronic only]
Focal power. Hartwig, Robert E.; Maroulas, John — 2005 ELA. The Electronic Journal of Linear Algebra [electronic only]