Minus k-subdomination in graphs II. - Johannes H. Hattingh; Elna Ungerer (Discret. Math., 1997)

Minus k-subdomination in graphs III. - Johannes H. Hattingh; Alice A. McRae; Elna Ungerer (Australas. J Comb., 1998)

Partial signed domination in graphs. - Johannes H. Hattingh; Elna Ungerer; Michael A. Henning (Ars Comb., 1998)

The signed and minus k-subdomination numbers of comets. - Johannes H. Hattingh; Elna Ungerer (Discret. Math., 1998)

On parameters related to strong and weak domination in graphs. - Gayla S. Domke; Johannes H. Hattingh; Lisa R. Markus; Elna Ungerer (Discret. Math., 2002)