Random Context Languages. - Andries P. J. van der Walt (IFIP Congress (1), 1971)

Locally Linear Families of Languages - Andries P. J. van der Walt (Inf. Control., 1976)

Generating Pictures Using Random Forbidding Context. - Sigrid Ewert; Andries P. J. van der Walt (Int. J. Pattern Recognit. Artif. Intell., 1998)

A Hierarchy Result for Random Forbidding Context Picture Grammars. - Sigrid Ewert; Andries P. J. van der Walt (Int. J. Pattern Recognit. Artif. Intell., 1999)

Generating Pictures Using Random Permitting Context. - Sigrid Ewert; Andries P. J. van der Walt (Int. J. Pattern Recognit. Artif. Intell., 1999)

Shrink Indecomposable Fractals. - Sigrid Ewert; Andries P. J. van der Walt (J. Univers. Comput. Sci., 1999)

A shrinking lemma for random forbidding context languages. - Andries P. J. van der Walt; Sigrid Ewert (Theor. Comput. Sci., 2000)

A pumping lemma for random permitting context languages. - Sigrid Ewert; Andries P. J. van der Walt (Theor. Comput. Sci., 2002)

The Power and Limitations of Random Context. - Sigrid Ewert; Andries P. J. van der Walt (Grammars and Automata for String Processing, 2003)

A property of random context picture grammars. - Andries P. J. van der Walt; Sigrid Ewert (Theor. Comput. Sci., 2003)

Random context tree grammars and tree transducers. - Frank Drewes; Christine du Toit; Sigrid Ewert; Johanna Högberg; Brink van der Merwe; Andries P. J. van der Walt (South Afr. Comput. J., 2005)

Bag Context Tree Grammars. - Frank Drewes; Christine du Toit; Sigrid Ewert; Brink van der Merwe; Andries P. J. van der Walt (Developments in Language Theory, 2006)

Necessary conditions for subclasses of random context languages. - Sigrid Ewert; Andries P. J. van der Walt (Theor. Comput. Sci., 2013)