A Conceptual Model of Wayfinding Using Multiple Levels of Abstraction. - Sabine Timpf; Gary S. Volta; David W. Pollock; Max J. Egenhofer (Spatio-Temporal Reasoning, 1992)

Interaction with GIS Attribute Data Based on Categorial Coverages. - Gary S. Volta; Max J. Egenhofer (COSIT, 1993)

Formalization of Families of Categorical Coverages. - Andrew U. Frank; Gary S. Volta; Matthew McGranaghan (Int. J. Geogr. Inf. Sci., 1997)