PETERSON, M. P. Creating Unclassed Choropleth Maps with PostScript. Cartographic Perspectives, [S. l.], n. 12, p. 4–6, 1992. DOI: 10.14714/CP12.1028. Disponível em: https://cartographicperspectives.org/index.php/journal/article/view/cp12-peterson. Acesso em: 4 may. 2026.